docs: updated to new auth challenge format and removed stale TOCTOU race condition note

IMPLEMENTATION.md

@@ -29,38 +29,23 @@ flowchart TD
     A([Client connects]) --> B[Receive AuthChallengeRequest]
     B --> C{pubkey in DB?}
 
-    C -- yes --> D[Read nonce\nIncrement nonce in DB]
-    D --> G
+    C -- yes --> G[Generate AuthChallenge]
 
     C -- no --> E[Ask all UserAgents:\nClientConnectionRequest]
     E --> F{First response}
     F -- denied --> Z([Reject connection])
     F -- approved --> F2[Cancel remaining\nUserAgent requests]
-    F2 --> F3[INSERT client\nnonce = 1]
-    F3 --> G[Send AuthChallenge\nwith nonce]
+    F2 --> F3[INSERT client]
+    F3 --> G
 
-    G --> H[Receive AuthChallengeSolution]
-    H --> I{Signature valid?}
-    I -- no --> Z
-    I -- yes --> J([Session started])
+    G --> H[Send AuthChallenge\ntimestamp + random bytes]
+    H --> I[Receive AuthChallengeSolution]
+    I --> K{Signature valid?}
+    K -- no --> Z
+    K -- yes --> J([Session started])
 ```
 
-### Known Issue: Concurrent Registration Race (TOCTOU)
-
-Two connections presenting the same previously-unknown public key can race through the approval flow simultaneously:
-
-1. Both check the DB → neither is registered.
-2. Both request approval from user agents → both receive approval.
-3. Both `INSERT` the client record → the second insert silently overwrites the first, resetting the nonce.
-
-This means the first connection's nonce is invalidated by the second, causing its challenge verification to fail. A fix requires either serialising new-client registration (e.g. an in-memory lock keyed on pubkey) or replacing the separate check + insert with an `INSERT OR IGNORE` / upsert guarded by a unique constraint on `public_key`.
-
-### Nonce Semantics
-
-The `program_client.nonce` column stores the **next usable nonce** — i.e. it is always one ahead of the nonce last issued in a challenge.
-
-- **New client:** inserted with `nonce = 1`; the first challenge is issued with `nonce = 0`.
-- **Existing client:** the current DB value is read and used as the challenge nonce, then immediately incremented within the same exclusive transaction, preventing replay.
+Auth challenges are generated from fresh random bytes plus a timestamp. They are signed as the canonical challenge payload and are not persisted in `program_client`.
 
 ---
 

protobufs/client/auth.proto

@@ -10,8 +10,8 @@ message AuthChallengeRequest {
 }
 
 message AuthChallenge {
-  bytes pubkey = 1;
-  int32 nonce = 2;
+  uint64 timestamp_nanos = 1;
+  bytes random = 2;
 }
 
 message AuthChallengeSolution {

protobufs/user_agent/auth.proto

@@ -8,7 +8,8 @@ message AuthChallengeRequest {
 }
 
 message AuthChallenge {
-  int32 nonce = 1;
+  uint64 timestamp_nanos = 1;
+  bytes random = 2;
 }
 
 message AuthChallengeSolution {

server/Cargo.lock

@@ -683,6 +683,7 @@ dependencies = [
  "arbiter-crypto",
  "arbiter-proto",
  "async-trait",
+ "chrono",
  "http",
  "rand 0.10.1",
  "rustls-webpki",
@@ -696,7 +697,7 @@ dependencies = [
 name = "arbiter-crypto"
 version = "0.1.0"
 dependencies = [
- "base64",
+ "chrono",
  "memsafe",
  "ml-dsa",
  "rand 0.10.1",

server/crates/arbiter-client/Cargo.toml

@@ -24,3 +24,4 @@ http = "1.4.0"
 rustls-webpki = { version = "0.103.10", features = ["aws-lc-rs"] }
 async-trait.workspace = true
 rand.workspace = true
+chrono.workspace = true

server/crates/arbiter-client/src/auth.rs

@@ -1,4 +1,4 @@
-use arbiter_crypto::authn::{CLIENT_CONTEXT, SigningKey, format_challenge};
+use arbiter_crypto::authn::{self, CLIENT_CONTEXT, SigningKey};
 use arbiter_proto::{
     ClientMetadata,
     proto::{
@@ -15,6 +15,7 @@ use arbiter_proto::{
         shared::ClientInfo as ProtoClientInfo,
     },
 };
+use chrono::DateTime;
 
 use crate::{
     storage::StorageError,
@@ -23,6 +24,8 @@ use crate::{
 
 #[derive(Debug, thiserror::Error)]
 pub enum AuthError {
+    #[error("Server sent invalid auth challenge")]
+    InvalidChallenge,
     #[error("Auth challenge was not returned by server")]
     MissingAuthChallenge,
 
@@ -98,7 +101,15 @@ async fn send_auth_challenge_solution(
     key: &SigningKey,
     challenge: AuthChallenge,
 ) -> std::result::Result<(), AuthError> {
-    let challenge_payload = format_challenge(challenge.nonce, &challenge.pubkey);
+    let timestamp = DateTime::from_timestamp_nanos(challenge.timestamp_nanos as i64);
+    let challenge = authn::AuthChallenge {
+        nonce: *challenge
+            .random
+            .as_array()
+            .ok_or(AuthError::InvalidChallenge)?,
+        timestamp,
+    };
+    let challenge_payload: Vec<u8> = challenge.format();
     let signature = key
         .sign_message(&challenge_payload, CLIENT_CONTEXT)
         .map_err(|_| AuthError::UnexpectedAuthResponse)?

server/crates/arbiter-crypto/Cargo.toml

@@ -6,14 +6,14 @@ edition = "2024"
 [dependencies]
 ml-dsa = {workspace = true, optional = true }
 rand = {workspace = true, optional = true}
-base64 = {workspace = true, optional = true }
 memsafe = {version = "0.4.0", optional = true}
 x-wing = { version = "0.1.0-rc.0", features = ["zeroize"] }
+chrono.workspace = true
 
 [lints]
 workspace = true
 
 [features]
 default = ["authn", "safecell"]
-authn = ["dep:ml-dsa", "dep:rand", "dep:base64"]
+authn = ["dep:ml-dsa", "dep:rand"]
 safecell = ["dep:memsafe"]

server/crates/arbiter-crypto/src/authn/v1.rs

@@ -1,17 +1,56 @@
 use std::hash::Hash;
 
-use base64::{Engine as _, prelude::BASE64_STANDARD};
+use chrono::{DateTime, Utc};
 use ml_dsa::{
     EncodedVerifyingKey, Error, KeyGen, MlDsa87, Seed, Signature as MlDsaSignature,
     SigningKey as MlDsaSigningKey, VerifyingKey as MlDsaVerifyingKey, signature::Keypair as _,
 };
+use rand::RngExt;
 
 pub static CLIENT_CONTEXT: &[u8] = b"arbiter_client";
 pub static USERAGENT_CONTEXT: &[u8] = b"arbiter_user_agent";
 
-pub fn format_challenge(nonce: i32, pubkey: &[u8]) -> Vec<u8> {
-    let concat_form = format!("{}:{}", nonce, BASE64_STANDARD.encode(pubkey));
-    concat_form.into_bytes()
+const NONCE_SIZE: usize = 32;
+
+#[derive(Debug, Clone)]
+pub struct AuthChallenge {
+    pub nonce: [u8; NONCE_SIZE],
+    pub timestamp: DateTime<Utc>,
+}
+
+impl AuthChallenge {
+    pub fn generate(rng: &mut impl rand::CryptoRng) -> Self {
+        let timestamp = Utc::now();
+        let nonce = {
+            let mut array = [0; NONCE_SIZE];
+            rng.fill(&mut array);
+            array
+        };
+
+        Self { nonce, timestamp }
+    }
+
+    pub fn format(&self) -> Vec<u8> {
+        {
+            let mut buffer = Vec::from(self.nonce);
+
+            let stamp = self
+                .timestamp
+                .timestamp_nanos_opt()
+                .expect("We would be long dead by the time this triggers :)");
+            buffer.extend_from_slice(stamp.to_be_bytes().as_slice());
+
+            buffer
+        }
+    }
+
+    pub fn from_parts(nonce: &[u8], timestamp: i64) -> Result<Self, ()> {
+        let random_nonce = nonce.as_array().ok_or(())?;
+        Ok(AuthChallenge {
+            nonce: *random_nonce,
+            timestamp: DateTime::from_timestamp_nanos(timestamp),
+        })
+    }
 }
 
 pub type KeyParams = MlDsa87;
@@ -36,12 +75,10 @@ impl PublicKey {
         self.0.encode().to_vec()
     }
 
-    pub fn verify(&self, nonce: i32, context: &[u8], signature: &Signature) -> bool {
-        self.0.verify_with_context(
-            &format_challenge(nonce, &self.to_bytes()),
-            context,
-            &signature.0,
-        )
+    pub fn verify(&self, challenge: &AuthChallenge, context: &[u8], signature: &Signature) -> bool {
+        let challenge = challenge.format();
+        self.0
+            .verify_with_context(&challenge, context, &signature.0)
     }
 }
 
@@ -75,11 +112,14 @@ impl SigningKey {
             .map(Into::into)
     }
 
-    pub fn sign_challenge(&self, nonce: i32, context: &[u8]) -> Result<Signature, Error> {
-        self.sign_message(
-            &format_challenge(nonce, &self.public_key().to_bytes()),
-            context,
-        )
+    pub fn sign_challenge(
+        &self,
+        challenge: &AuthChallenge,
+        context: &[u8],
+    ) -> Result<Signature, Error> {
+        let challenge = challenge.format();
+
+        self.sign_message(&challenge, context)
     }
 }
 
@@ -140,6 +180,8 @@ impl TryFrom<&'_ [u8]> for Signature {
 mod tests {
     use ml_dsa::{KeyGen, MlDsa87, signature::Keypair as _};
 
+    use crate::authn::AuthChallenge;
+
     use super::{CLIENT_CONTEXT, PublicKey, Signature, SigningKey, USERAGENT_CONTEXT};
 
     #[test]
@@ -169,13 +211,13 @@ mod tests {
     fn challenge_verification_uses_context_and_canonical_key_bytes() {
         let key = SigningKey::generate();
         let public_key = key.public_key();
-        let nonce = 17;
+        let challenge = AuthChallenge::generate(&mut rand::rng());
         let signature = key
-            .sign_challenge(nonce, CLIENT_CONTEXT)
+            .sign_challenge(&challenge, CLIENT_CONTEXT)
             .expect("signature should be created");
 
-        assert!(public_key.verify(nonce, CLIENT_CONTEXT, &signature));
-        assert!(!public_key.verify(nonce, USERAGENT_CONTEXT, &signature));
+        assert!(public_key.verify(&challenge, CLIENT_CONTEXT, &signature));
+        assert!(!public_key.verify(&challenge, USERAGENT_CONTEXT, &signature));
     }
 
     #[test]
@@ -185,10 +227,16 @@ mod tests {
 
         assert_eq!(restored.public_key(), original.public_key());
 
+        let challenge = AuthChallenge::generate(&mut rand::rng());
+
         let signature = restored
-            .sign_challenge(9, CLIENT_CONTEXT)
+            .sign_challenge(&challenge, CLIENT_CONTEXT)
             .expect("signature should be created");
 
-        assert!(restored.public_key().verify(9, CLIENT_CONTEXT, &signature));
+        assert!(
+            restored
+                .public_key()
+                .verify(&challenge, CLIENT_CONTEXT, &signature)
+        );
     }
 }

server/crates/arbiter-proto/src/transport.rs

@@ -58,6 +58,7 @@
 use std::marker::PhantomData;
 
 use async_trait::async_trait;
+use kameo::{error::Infallible, prelude::*};
 
 /// Errors returned by transport adapters implementing [`Bi`].
 #[derive(thiserror::Error, Debug)]
@@ -191,3 +192,29 @@ where
 }
 
 pub mod grpc;
+
+#[derive(thiserror::Error, Debug)]
+pub enum ForwardError<I> {
+    #[error("Transport error: {0}")]
+    Transport(#[from] Error),
+    #[error("Actor delivery error: {0}")]
+    Actor(SendError<I>),
+}
+
+pub async fn forward_to_actor<Transport, Inbound, Outbound, Handler>(
+    transport: &mut Transport,
+    actor: &ActorRef<Handler>,
+) -> Result<(), ForwardError<Inbound>>
+where
+    Transport: Bi<Inbound, <Outbound as Reply>::Ok>,
+    Handler: Actor + Message<Inbound, Reply = Outbound>,
+    Inbound: Send + 'static,
+    Outbound: Send + 'static + Reply<Error = Infallible>, // `Infallible` to enforce contract that `Outbound` carries handler-level error
+{
+    while let Some(request) = transport.recv().await {
+        let resp = actor.ask(request).await.map_err(ForwardError::Actor)?;
+        transport.send(resp).await?
+    }
+
+    Err(Error::ChannelClosed.into())
+}

server/crates/arbiter-server/migrations/2026-02-14-171124-0000_init/up.sql

@@ -45,13 +45,11 @@ insert into arbiter_settings (id) values (1) on conflict do nothing;
 
 create table if not exists useragent_client (
     id integer not null primary key,
-    nonce integer not null default(1), -- used for auth challenge
     public_key blob not null,
-    key_type integer not null default(1),
     created_at integer not null default(unixepoch ('now')),
     updated_at integer not null default(unixepoch ('now'))
 ) STRICT;
-create unique index if not exists uniq_useragent_client_public_key on useragent_client (public_key, key_type);
+create unique index if not exists uniq_useragent_client_public_key on useragent_client (public_key);
 
 create table if not exists client_metadata (
     id integer not null primary key,
@@ -73,7 +71,6 @@ create unique index if not exists uniq_metadata_binding_client on client_metadat
 
 create table if not exists program_client (
     id integer not null primary key,
-    nonce integer not null default(1), -- used for auth challenge
     public_key blob not null,
     metadata_id integer not null references client_metadata (id) on delete cascade,
     created_at integer not null default(unixepoch ('now')),

server/crates/arbiter-server/src/actors/flow_coordinator/mod.rs

@@ -10,19 +10,27 @@ use kameo::{
 use tracing::info;
 
 use crate::{
-    actors::flow_coordinator::client_connect_approval::ClientApprovalController,
-    peers::{
-        client::{ClientProfile, session::ClientSession},
-        user_agent::UserAgentSession,
+    actors::{
+        flow_coordinator::client_connect_approval::ClientApprovalController,
+        useragent_registry::{GetConnected, UserAgentRegistry},
     },
+    peers::client::{ClientProfile, session::ClientSession},
 };
 
 pub mod client_connect_approval;
 
-#[derive(Default)]
 pub struct FlowCoordinator {
-    pub user_agents: HashMap<ActorId, ActorRef<UserAgentSession>>,
     pub clients: HashMap<ActorId, ActorRef<ClientSession>>,
+    useragent_registry: ActorRef<UserAgentRegistry>,
+}
+
+impl FlowCoordinator {
+    pub fn new(useragent_registry: ActorRef<UserAgentRegistry>) -> Self {
+        Self {
+            clients: HashMap::default(),
+            useragent_registry,
+        }
+    }
 }
 
 impl Actor for FlowCoordinator {
@@ -40,13 +48,7 @@ impl Actor for FlowCoordinator {
         id: ActorId,
         _: ActorStopReason,
     ) -> Result<ControlFlow<ActorStopReason>, Self::Error> {
-        if self.user_agents.remove(&id).is_some() {
-            info!(
-                ?id,
-                actor = "FlowCoordinator",
-                event = "useragent.disconnected"
-            );
-        } else if self.clients.remove(&id).is_some() {
+        if self.clients.remove(&id).is_some() {
             info!(
                 ?id,
                 actor = "FlowCoordinator",
@@ -71,17 +73,6 @@ pub enum ApprovalError {
 
 #[messages]
 impl FlowCoordinator {
-    #[message(ctx)]
-    pub async fn register_user_agent(
-        &mut self,
-        actor: ActorRef<UserAgentSession>,
-        ctx: &mut Context<Self, ()>,
-    ) {
-        info!(id = %actor.id(), actor = "FlowCoordinator", event = "useragent.connected");
-        ctx.actor_ref().link(&actor).await;
-        self.user_agents.insert(actor.id(), actor);
-    }
-
     #[message(ctx)]
     pub async fn register_client(
         &mut self,
@@ -103,7 +94,14 @@ impl FlowCoordinator {
             unreachable!("Expected `request_client_approval` to have callback channel");
         };
 
-        let refs: Vec<_> = self.user_agents.values().cloned().collect();
+        let refs = match self.useragent_registry.ask(GetConnected).await {
+            Ok(refs) => refs,
+            Err(_) => {
+                reply_sender.send(Err(ApprovalError::NoUserAgentsConnected));
+                return reply;
+            }
+        };
+
         if refs.is_empty() {
             reply_sender.send(Err(ApprovalError::NoUserAgentsConnected));
             return reply;

server/crates/arbiter-server/src/actors/mod.rs

@@ -4,7 +4,11 @@ use thiserror::Error;
 
 use crate::{
     actors::{
-        bootstrap::Bootstrapper, evm::EvmActor, flow_coordinator::FlowCoordinator, vault::Vault,
+        bootstrap::Bootstrapper,
+        evm::EvmActor,
+        flow_coordinator::FlowCoordinator,
+        useragent_registry::UserAgentRegistry,
+        vault::Vault,
     },
     db,
 };
@@ -30,6 +34,7 @@ pub struct GlobalActors {
     pub vault: ActorRef<Vault>,
     pub bootstrapper: ActorRef<Bootstrapper>,
     pub flow_coordinator: ActorRef<FlowCoordinator>,
+    pub useragent_registry: ActorRef<UserAgentRegistry>,
     pub evm: ActorRef<EvmActor>,
     pub events: ActorRef<MessageBus>,
 }
@@ -42,11 +47,15 @@ impl GlobalActors {
     pub async fn spawn(db: db::DatabasePool) -> Result<Self, SpawnError> {
         let message_bus = Self::spawn_message_bus();
         let key_holder = Vault::spawn(Vault::new(db.clone(), message_bus.clone()).await?);
+        let useragent_registry = UserAgentRegistry::spawn(UserAgentRegistry::default());
         Ok(Self {
             bootstrapper: Bootstrapper::spawn(Bootstrapper::new(&db).await?),
             evm: EvmActor::spawn(EvmActor::new(key_holder.clone(), db)),
             vault: key_holder,
-            flow_coordinator: FlowCoordinator::spawn(FlowCoordinator::default()),
+            flow_coordinator: FlowCoordinator::spawn(FlowCoordinator::new(
+                useragent_registry.clone(),
+            )),
+            useragent_registry,
             events: message_bus,
         })
     }

server/crates/arbiter-server/src/actors/useragent_registry.rs

@@ -1,57 +1,58 @@
-use alloy::primitives::map::HashMap;
-use arbiter_crypto::authn;
-use kameo::{error::Infallible, prelude::*};
+use std::{collections::HashMap, ops::ControlFlow};
 
-use crate::{db::DatabasePool, peers::user_agent::{Credentials, UserAgentSession}};
+use kameo::{
+    Actor,
+    actor::{ActorId, ActorRef},
+    error::Infallible,
+    messages,
+    prelude::{ActorStopReason, Context, WeakActorRef},
+};
+use tracing::info;
 
-use super::vault::{Vault, events as vault_events};
-
-pub struct Args {
-    pub vault: ActorRef<Vault>,
-    pub pool: DatabasePool,
-}
+use crate::peers::user_agent::UserAgentSession;
 
+#[derive(Default)]
 pub struct UserAgentRegistry {
-    vault: ActorRef<Vault>,
-    pool: DatabasePool,
-    connected: HashMap<Credentials, ActorRef<UserAgentSession>>,
+    connected: HashMap<ActorId, ActorRef<UserAgentSession>>,
 }
 
-impl Message<vault_events::Bootstrapped> for UserAgentRegistry {
-    type Reply = ();
-
-    async fn handle(
-        &mut self,
-        msg: vault_events::Bootstrapped,
-        ctx: &mut Context<Self, Self::Reply>,
-    ) -> Self::Reply {
-        todo!()
-    }
-}
-
-impl Message<vault_events::Unsealed> for UserAgentRegistry {
-    type Reply = ();
-
-    async fn handle(
-        &mut self,
-        msg: vault_events::Unsealed,
-        ctx: &mut Context<Self, Self::Reply>,
-    ) -> Self::Reply {
-        todo!()
-    }
-}
 impl Actor for UserAgentRegistry {
-    type Args = Args;
+    type Args = Self;
 
     type Error = Infallible;
 
-    async fn on_start(args: Self::Args, actor_ref: ActorRef<Self>) -> Result<Self, Self::Error> {
-        Ok(Self {
-            vault: args.vault,
-            pool: args.pool,
-            connected: HashMap::default(),
-        })
+    async fn on_start(args: Self::Args, _: ActorRef<Self>) -> Result<Self, Self::Error> {
+        Ok(args)
     }
 
-    
+    async fn on_link_died(
+        &mut self,
+        _: WeakActorRef<Self>,
+        id: ActorId,
+        _: ActorStopReason,
+    ) -> Result<ControlFlow<ActorStopReason>, Self::Error> {
+        if self.connected.remove(&id).is_some() {
+            info!(?id, actor = "UserAgentRegistry", event = "useragent.disconnected");
+        }
+        Ok(ControlFlow::Continue(()))
+    }
+}
+
+#[messages]
+impl UserAgentRegistry {
+    #[message(ctx)]
+    pub async fn connect_useragent(
+        &mut self,
+        actor: ActorRef<UserAgentSession>,
+        ctx: &mut Context<Self, ()>,
+    ) {
+        info!(id = %actor.id(), actor = "UserAgentRegistry", event = "useragent.connected");
+        ctx.actor_ref().link(&actor).await;
+        self.connected.insert(actor.id(), actor);
+    }
+
+    #[message]
+    pub fn get_connected(&self) -> Vec<ActorRef<UserAgentSession>> {
+        self.connected.values().cloned().collect()
+    }
 }

server/crates/arbiter-server/src/db/models.rs

@@ -195,7 +195,6 @@ pub struct ProgramClientMetadataHistory {
 #[diesel(table_name = schema::program_client, check_for_backend(Sqlite))]
 pub struct ProgramClient {
     pub id: i32,
-    pub nonce: i32,
     pub public_key: Vec<u8>,
     pub metadata_id: i32,
     pub created_at: SqliteTimestamp,
@@ -206,7 +205,6 @@ pub struct ProgramClient {
 #[diesel(table_name = schema::useragent_client, check_for_backend(Sqlite))]
 pub struct UseragentClient {
     pub id: i32,
-    pub nonce: i32,
     pub public_key: Vec<u8>,
     pub created_at: SqliteTimestamp,
     pub updated_at: SqliteTimestamp,

server/crates/arbiter-server/src/db/schema.rs

@@ -155,7 +155,6 @@ diesel::table! {
 diesel::table! {
     program_client (id) {
         id -> Integer,
-        nonce -> Integer,
         public_key -> Binary,
         metadata_id -> Integer,
         created_at -> Integer,
@@ -189,9 +188,7 @@ diesel::table! {
 diesel::table! {
     useragent_client (id) {
         id -> Integer,
-        nonce -> Integer,
         public_key -> Binary,
-        key_type -> Integer,
         created_at -> Integer,
         updated_at -> Integer,
     }

server/crates/arbiter-server/src/grpc/client/auth.rs

@@ -44,10 +44,14 @@ impl<'a> AuthTransportAdapter<'a> {
 
     fn response_to_proto(response: auth::Outbound) -> AuthResponsePayload {
         match response {
-            auth::Outbound::AuthChallenge { pubkey, nonce } => {
+            auth::Outbound::AuthChallenge {  challenge } => {
                 AuthResponsePayload::Challenge(ProtoAuthChallenge {
-                    pubkey: pubkey.to_bytes(),
-                    nonce,
+                    timestamp_nanos: challenge
+                        .timestamp
+                        .timestamp_nanos_opt()
+                        .expect("timestamp within range")
+                        as u64,
+                    random: challenge.nonce.to_vec(),
                 })
             }
             auth::Outbound::AuthSuccess => {

server/crates/arbiter-server/src/grpc/user_agent.rs

@@ -1,4 +1,4 @@
-use tokio::sync::{mpsc, oneshot};
+use tokio::sync::mpsc;
 
 use arbiter_proto::{
     proto::user_agent::{
@@ -9,17 +9,13 @@ use arbiter_proto::{
     transport::{Error as TransportError, Receiver, Sender, grpc::GrpcBi},
 };
 use async_trait::async_trait;
-use kameo::actor::{ActorRef, Spawn as _};
+use kameo::actor::ActorRef;
 use tonic::Status;
 use tracing::{error, info, warn};
 
 use crate::{
-    crypto::integrity,
     grpc::request_tracker::RequestTracker,
-    peers::user_agent::{
-        Credentials, OutOfBand, UserAgentConnection, UserAgentSession,
-        vault_gate::VaultGate,
-    },
+    peers::user_agent::{OutOfBand, UserAgentConnection, UserAgentSession},
 };
 
 mod auth;
@@ -129,115 +125,23 @@ pub async fn start(
 ) {
     let mut request_tracker = RequestTracker::default();
 
-    let auth_creds = match auth::start(&mut conn, &mut bi, &mut request_tracker).await {
-        Ok(creds) => creds,
-        Err(e) => {
-            warn!(error = ?e, "Authentication failed");
-            return;
-        }
-    };
-
-    info!(pubkey = ?auth_creds.creds.pubkey, "User authenticated successfully");
-
-    let creds = if integrity::is_signing_available(&conn.actors.vault)
-        .await
-        .unwrap_or(false)
-    {
-        // Vault is unsealed; integrity was verified during auth — promote directly.
-        auth_creds.creds
-    } else {
-        // Vault is sealed/unbootstrapped; run the VaultGate phase.
-        let (promotion_tx, promotion_rx) = oneshot::channel();
-        let gate = VaultGate::spawn(VaultGate::new(
-            auth_creds,
-            conn.actors.clone(),
-            conn.db.clone(),
-            promotion_tx,
-        ));
-
-        let result = vault_gate_loop(&mut bi, &gate, &mut request_tracker, promotion_rx).await;
-        gate.kill();
-
-        match result {
-            Some(creds) => creds,
-            None => return,
-        }
-    };
-
     let (oob_sender, oob_receiver) = mpsc::channel(16);
     let oob_adapter = OutOfBandAdapter(oob_sender);
 
-    let actor = UserAgentSession::spawn(UserAgentSession::new(conn, creds, Box::new(oob_adapter)));
-    let actor_for_cleanup = actor.clone();
-
-    dispatch_loop(bi, actor, oob_receiver, request_tracker).await;
-    actor_for_cleanup.kill();
+    let actor = {
+        let transport = auth::AuthTransportAdapter::new(&mut bi, &mut request_tracker);
+        match crate::peers::user_agent::start(&mut conn, transport, Box::new(oob_adapter)).await {
+            Ok(actor) => actor,
+            Err(e) => {
+                warn!(error = ?e, "User agent connection failed");
+                return;
             }
-
-async fn vault_gate_loop(
-    bi: &mut GrpcBi<UserAgentRequest, UserAgentResponse>,
-    gate: &ActorRef<VaultGate>,
-    request_tracker: &mut RequestTracker,
-    mut promotion_rx: oneshot::Receiver<Result<Credentials, crate::peers::user_agent::vault_gate::Error>>,
-) -> Option<Credentials> {
-    loop {
-        tokio::select! {
-            result = &mut promotion_rx => {
-                return match result {
-                    Ok(Ok(creds)) => Some(creds),
-                    Ok(Err(e)) => {
-                        warn!(error = ?e, "VaultGate promotion failed");
-                        None
-                    }
-                    Err(_) => {
-                        warn!("VaultGate promotion channel closed unexpectedly");
-                        None
-                    }
-                };
-            }
-
-            message = bi.recv() => {
-                let Some(message) = message else { return None; };
-
-                let conn = match message {
-                    Ok(conn) => conn,
-                    Err(err) => {
-                        warn!(error = ?err, "Failed to receive request during vault gate phase");
-                        return None;
         }
     };
 
-                let request_id = match request_tracker.request(conn.id) {
-                    Ok(id) => id,
-                    Err(err) => {
-                        let _ = bi.send(Err(err)).await;
-                        return None;
-                    }
-                };
+    info!("User agent session established");
 
-                let Some(payload) = conn.payload else {
-                    let _ = bi.send(Err(Status::invalid_argument("Missing request payload"))).await;
-                    return None;
-                };
+    dispatch_loop(bi, actor.clone(), oob_receiver, request_tracker).await;
+    actor.kill();
+}
 
-                let response = match payload {
-                    UserAgentRequestPayload::Vault(req) => vault_gate::dispatch(gate, req).await,
-                    _ => Err(Status::permission_denied("Only vault operations are permitted before unsealing")),
-                };
-
-                match response {
-                    Ok(Some(payload)) => {
-                        if bi.send(Ok(UserAgentResponse { id: Some(request_id), payload: Some(payload) })).await.is_err() {
-                            return None;
-                        }
-                    }
-                    Ok(None) => {}
-                    Err(status) => {
-                        let _ = bi.send(Err(status)).await;
-                        return None;
-                    }
-                }
-            }
-        }
-    }
-}

server/crates/arbiter-server/src/grpc/user_agent/auth.rs

@@ -19,7 +19,7 @@ use tracing::warn;
 
 use crate::{
     grpc::request_tracker::RequestTracker,
-    peers::user_agent::{AuthCredentials, UserAgentConnection, auth},
+    peers::user_agent::{Credentials, UserAgentConnection, auth},
 };
 
 pub struct AuthTransportAdapter<'a> {
@@ -77,8 +77,15 @@ impl Sender<Result<auth::Outbound, auth::Error>> for AuthTransportAdapter<'_> {
     ) -> Result<(), TransportError> {
         use auth::{Error, Outbound};
         let payload = match item {
-            Ok(Outbound::AuthChallenge { nonce }) => {
-                AuthResponsePayload::Challenge(ProtoAuthChallenge { nonce })
+            Ok(Outbound::AuthChallenge { challenge }) => {
+                AuthResponsePayload::Challenge(ProtoAuthChallenge {
+                    timestamp_nanos: challenge
+                        .timestamp
+                        .timestamp_nanos_opt()
+                        .expect("timestamp within range")
+                        as u64,
+                    random: challenge.nonce.to_vec(),
+                })
             }
             Ok(Outbound::AuthSuccess) => {
                 AuthResponsePayload::Result(ProtoAuthResult::Success.into())
@@ -183,7 +190,7 @@ pub async fn start(
     conn: &mut UserAgentConnection,
     bi: &mut GrpcBi<UserAgentRequest, UserAgentResponse>,
     request_tracker: &mut RequestTracker,
-) -> Result<AuthCredentials, auth::Error> {
+) -> Result<Credentials, auth::Error> {
     let mut transport = AuthTransportAdapter::new(bi, request_tracker);
     auth::authenticate(conn, &mut transport).await
 }

server/crates/arbiter-server/src/grpc/user_agent/vault_gate.rs

@@ -1,57 +1,16 @@
-use arbiter_proto::{
-    proto::user_agent::{
-        user_agent_request::Payload as UserAgentRequestPayload,
-        user_agent_response::Payload as UserAgentResponsePayload,
-        vault::{
-            self as proto_vault,
-            bootstrap::{self as proto_bootstrap, BootstrapResult as ProtoBootstrapResult},
-            request::Payload as VaultRequestPayload,
-            response::Payload as VaultResponsePayload,
-            unseal::{
-                self as proto_unseal, UnsealResult as ProtoUnsealResult,
-                request::Payload as UnsealRequestPayload,
-                response::Payload as UnsealResponsePayload,
-            },
-        },
-    },
-    transport::{Bi, Error as TransportError, Receiver, Sender},
-};
+use arbiter_proto::transport::{Bi, Error as TransportError, Receiver, Sender};
 use async_trait::async_trait;
 use tonic::Status;
 use tracing::warn;
 
 use super::auth::AuthTransportAdapter;
-use crate::peers::user_agent::vault_gate::{
-    self as vault_gate, HandleBootstrapEncryptedKey, HandleHandshake, HandleUnsealEncryptedKey,
+use crate::{
+    grpc::TryConvert,
+    peers::user_agent::vault_gate::{self as vault_gate},
 };
 
-fn wrap_vault_response(payload: VaultResponsePayload) -> UserAgentResponsePayload {
-    UserAgentResponsePayload::Vault(proto_vault::Response {
-        payload: Some(payload),
-    })
-}
-
-fn wrap_unseal_response(payload: UnsealResponsePayload) -> UserAgentResponsePayload {
-    wrap_vault_response(VaultResponsePayload::Unseal(proto_unseal::Response {
-        payload: Some(payload),
-    }))
-}
-
-fn wrap_bootstrap_response(result: ProtoBootstrapResult) -> UserAgentResponsePayload {
-    wrap_vault_response(VaultResponsePayload::Bootstrap(proto_bootstrap::Response {
-        result: result.into(),
-    }))
-}
-
-impl AuthTransportAdapter<'_> {
-    async fn send_query_state(&mut self) -> Result<(), TransportError> {
-        use arbiter_proto::proto::shared::VaultState as ProtoVaultState;
-        self.send_response_payload(wrap_vault_response(VaultResponsePayload::State(
-            ProtoVaultState::Sealed.into(),
-        )))
-        .await
-    }
-}
+mod inbound;
+mod outbound;
 
 #[async_trait]
 impl Receiver<vault_gate::Inbound> for AuthTransportAdapter<'_> {
@@ -60,7 +19,10 @@ impl Receiver<vault_gate::Inbound> for AuthTransportAdapter<'_> {
             let request = match self.bi_mut().recv().await? {
                 Ok(request) => request,
                 Err(error) => {
-                    warn!(?error, "Failed to receive user agent request during vault gate");
+                    warn!(
+                        ?error,
+                        "Failed to receive user agent request during vault gate"
+                    );
                     return None;
                 }
             };
@@ -78,86 +40,12 @@ impl Receiver<vault_gate::Inbound> for AuthTransportAdapter<'_> {
                 return None;
             };
 
-            let vault_req = match payload {
-                UserAgentRequestPayload::Vault(req) => req,
-                _ => {
-                    let _ = self
-                        .bi_mut()
-                        .send(Err(Status::permission_denied(
-                            "Only vault operations are permitted before unsealing",
-                        )))
-                        .await;
+            match payload.try_convert() {
+                Ok(inbound) => return Some(inbound),
+                Err(status) => {
+                    let _ = self.bi_mut().send(Err(status)).await;
                     return None;
                 }
-            };
-
-            let Some(vault_payload) = vault_req.payload else {
-                let _ = self
-                    .bi_mut()
-                    .send(Err(Status::invalid_argument("Missing vault request payload")))
-                    .await;
-                return None;
-            };
-
-            match vault_payload {
-                VaultRequestPayload::QueryState(_) => {
-                    if self.send_query_state().await.is_err() {
-                        return None;
-                    }
-                    continue;
-                }
-                VaultRequestPayload::Unseal(req) => {
-                    let Some(unseal_payload) = req.payload else {
-                        let _ = self
-                            .bi_mut()
-                            .send(Err(Status::invalid_argument("Missing unseal request payload")))
-                            .await;
-                        return None;
-                    };
-                    match unseal_payload {
-                        UnsealRequestPayload::Start(start) => {
-                            let Ok(bytes) = <[u8; 32]>::try_from(start.client_pubkey) else {
-                                let _ = self
-                                    .bi_mut()
-                                    .send(Err(Status::invalid_argument(
-                                        "Invalid X25519 public key",
-                                    )))
-                                    .await;
-                                return None;
-                            };
-                            return Some(vault_gate::Inbound::HandleHandshake(HandleHandshake {
-                                client_pubkey: x25519_dalek::PublicKey::from(bytes),
-                            }));
-                        }
-                        UnsealRequestPayload::EncryptedKey(key) => {
-                            return Some(vault_gate::Inbound::HandleUnsealEncryptedKey(
-                                HandleUnsealEncryptedKey {
-                                    nonce: key.nonce,
-                                    ciphertext: key.ciphertext,
-                                    associated_data: key.associated_data,
-                                },
-                            ));
-                        }
-                    }
-                }
-                VaultRequestPayload::Bootstrap(req) => {
-                    let Some(encrypted_key) = req.encrypted_key else {
-                        let _ = self
-                            .bi_mut()
-                            .send(Err(Status::invalid_argument(
-                                "Missing bootstrap encrypted key",
-                            )))
-                            .await;
-                        return None;
-                    };
-                    return Some(vault_gate::Inbound::HandleBootstrapEncryptedKey(
-                        HandleBootstrapEncryptedKey {
-                            nonce: encrypted_key.nonce,
-                            ciphertext: encrypted_key.ciphertext,
-                            associated_data: encrypted_key.associated_data,
-                        },
-                    ));
-                }
             }
         }
     }
@@ -180,55 +68,10 @@ impl Sender<Result<vault_gate::Outbound, vault_gate::Error>> for AuthTransportAd
             }
         };
 
-        let payload = match outbound {
-            vault_gate::Outbound::HandleHandshake(Ok(response)) => {
-                wrap_unseal_response(UnsealResponsePayload::Start(
-                    proto_unseal::UnsealStartResponse {
-                        server_pubkey: response.server_pubkey.as_bytes().to_vec(),
-                    },
-                ))
+        match outbound.try_convert() {
+            Ok(payload) => self.send_response_payload(payload).await,
+            Err(status) => self.bi_mut().send(Err(status)).await,
         }
-            vault_gate::Outbound::HandleHandshake(Err(err)) => {
-                warn!(?err, "handshake failed");
-                return self
-                    .bi_mut()
-                    .send(Err(Status::internal("Failed to start unseal flow")))
-                    .await;
-            }
-            vault_gate::Outbound::HandleUnsealEncryptedKey(result) => {
-                let proto_result = match result {
-                    Ok(()) => ProtoUnsealResult::Success,
-                    Err(vault_gate::Error::InvalidKey) => ProtoUnsealResult::InvalidKey,
-                    Err(err) => {
-                        warn!(?err, "unseal failed");
-                        return self
-                            .bi_mut()
-                            .send(Err(Status::internal("Failed to unseal vault")))
-                            .await;
-                    }
-                };
-                wrap_unseal_response(UnsealResponsePayload::Result(proto_result.into()))
-            }
-            vault_gate::Outbound::HandleBootstrapEncryptedKey(result) => {
-                let proto_result = match result {
-                    Ok(()) => ProtoBootstrapResult::Success,
-                    Err(vault_gate::Error::InvalidKey) => ProtoBootstrapResult::InvalidKey,
-                    Err(vault_gate::Error::AlreadyBootstrapped) => {
-                        ProtoBootstrapResult::AlreadyBootstrapped
-                    }
-                    Err(err) => {
-                        warn!(?err, "bootstrap failed");
-                        return self
-                            .bi_mut()
-                            .send(Err(Status::internal("Failed to bootstrap vault")))
-                            .await;
-                    }
-                };
-                wrap_bootstrap_response(proto_result)
-            }
-        };
-
-        self.send_response_payload(payload).await
     }
 }
 

server/crates/arbiter-server/src/grpc/user_agent/vault_gate/inbound.rs

@@ -0,0 +1,129 @@
+use arbiter_proto::proto::user_agent::{
+    user_agent_request::Payload as UserAgentRequestPayload,
+    vault::{
+        self as proto_vault,
+        bootstrap::{self as proto_bootstrap},
+        request::Payload as VaultRequestPayload,
+        unseal::{self as proto_unseal, request::Payload as UnsealRequestPayload},
+    },
+};
+use tonic::Status;
+
+use crate::{
+    grpc::{Convert, TryConvert},
+    peers::user_agent::vault_gate::{
+        self as vault_gate, HandleBootstrapEncryptedKey, HandleHandshake, HandleUnsealEncryptedKey,
+    },
+};
+
+impl TryConvert for UserAgentRequestPayload {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        match self {
+            UserAgentRequestPayload::Vault(req) => req.try_convert(),
+            _ => Err(Status::permission_denied(
+                "Only vault operations are permitted before unsealing",
+            )),
+        }
+    }
+}
+
+impl TryConvert for proto_vault::Request {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        self.payload
+            .ok_or_else(|| Status::invalid_argument("Missing vault request payload"))?
+            .try_convert()
+    }
+}
+
+impl TryConvert for VaultRequestPayload {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        match self {
+            VaultRequestPayload::QueryState(_) => Ok(vault_gate::Inbound::HandleVaultState),
+            VaultRequestPayload::Unseal(req) => req.try_convert(),
+            VaultRequestPayload::Bootstrap(req) => req.try_convert(),
+        }
+    }
+}
+
+impl TryConvert for proto_unseal::Request {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        self.payload
+            .ok_or_else(|| Status::invalid_argument("Missing unseal request payload"))?
+            .try_convert()
+    }
+}
+
+impl TryConvert for UnsealRequestPayload {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        match self {
+            UnsealRequestPayload::Start(start) => start.try_convert(),
+            UnsealRequestPayload::EncryptedKey(key) => Ok(key.convert()),
+        }
+    }
+}
+
+impl TryConvert for proto_unseal::UnsealStart {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        let bytes = <[u8; 32]>::try_from(self.client_pubkey)
+            .map_err(|_| Status::invalid_argument("Invalid X25519 public key"))?;
+        Ok(vault_gate::Inbound::HandleHandshake(HandleHandshake {
+            client_pubkey: x25519_dalek::PublicKey::from(bytes),
+        }))
+    }
+}
+
+impl Convert for proto_unseal::UnsealEncryptedKey {
+    type Output = vault_gate::Inbound;
+
+    fn convert(self) -> vault_gate::Inbound {
+        vault_gate::Inbound::HandleUnsealEncryptedKey(HandleUnsealEncryptedKey {
+            nonce: self.nonce,
+            ciphertext: self.ciphertext,
+            associated_data: self.associated_data,
+        })
+    }
+}
+
+impl TryConvert for proto_bootstrap::Request {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        self.encrypted_key
+            .ok_or_else(|| Status::invalid_argument("Missing bootstrap encrypted key"))?
+            .try_convert()
+    }
+}
+
+impl TryConvert for proto_bootstrap::BootstrapEncryptedKey {
+    type Output = vault_gate::Inbound;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<vault_gate::Inbound, Status> {
+        Ok(vault_gate::Inbound::HandleBootstrapEncryptedKey(
+            HandleBootstrapEncryptedKey {
+                nonce: self.nonce,
+                ciphertext: self.ciphertext,
+                associated_data: self.associated_data,
+            },
+        ))
+    }
+}

server/crates/arbiter-server/src/grpc/user_agent/vault_gate/outbound.rs

@@ -0,0 +1,115 @@
+use arbiter_proto::proto::{
+    shared::VaultState as ProtoVaultState,
+    user_agent::{
+        user_agent_response::Payload as UserAgentResponsePayload,
+        vault::{
+            self as proto_vault,
+            bootstrap::{self as proto_bootstrap, BootstrapResult as ProtoBootstrapResult},
+            response::Payload as VaultResponsePayload,
+            unseal::{
+                self as proto_unseal, UnsealResult as ProtoUnsealResult,
+                response::Payload as UnsealResponsePayload,
+            },
+        },
+    },
+};
+use tonic::Status;
+use tracing::warn;
+
+use crate::{
+    actors::vault::VaultState,
+    grpc::{Convert, TryConvert},
+    peers::user_agent::vault_gate::{self as vault_gate},
+};
+
+fn wrap_vault_response(payload: VaultResponsePayload) -> UserAgentResponsePayload {
+    UserAgentResponsePayload::Vault(proto_vault::Response {
+        payload: Some(payload),
+    })
+}
+
+fn wrap_unseal_response(payload: UnsealResponsePayload) -> UserAgentResponsePayload {
+    wrap_vault_response(VaultResponsePayload::Unseal(proto_unseal::Response {
+        payload: Some(payload),
+    }))
+}
+
+fn wrap_bootstrap_response(result: ProtoBootstrapResult) -> UserAgentResponsePayload {
+    wrap_vault_response(VaultResponsePayload::Bootstrap(proto_bootstrap::Response {
+        result: result.into(),
+    }))
+}
+
+impl Convert for VaultState {
+    type Output = UserAgentResponsePayload;
+
+    fn convert(self) -> UserAgentResponsePayload {
+        let proto_state = match self {
+            VaultState::Unbootstrapped => ProtoVaultState::Unbootstrapped,
+            VaultState::Sealed => ProtoVaultState::Sealed,
+            VaultState::Unsealed => ProtoVaultState::Unsealed,
+        };
+        wrap_vault_response(VaultResponsePayload::State(proto_state.into()))
+    }
+}
+
+impl Convert for vault_gate::HandshakeResponse {
+    type Output = UserAgentResponsePayload;
+
+    fn convert(self) -> UserAgentResponsePayload {
+        wrap_unseal_response(UnsealResponsePayload::Start(
+            proto_unseal::UnsealStartResponse {
+                server_pubkey: self.server_pubkey.as_bytes().to_vec(),
+            },
+        ))
+    }
+}
+
+impl TryConvert for vault_gate::Outbound {
+    type Output = UserAgentResponsePayload;
+    type Error = Status;
+
+    fn try_convert(self) -> Result<UserAgentResponsePayload, Status> {
+        match self {
+            vault_gate::Outbound::HandleVaultState(result) => result
+                .map_err(|err| {
+                    warn!(?err, "vault state query failed");
+                    Status::internal("Failed to query vault state")
+                })
+                .map(VaultState::convert),
+            vault_gate::Outbound::HandleHandshake(result) => result
+                .map_err(|err| {
+                    warn!(?err, "handshake failed");
+                    Status::internal("Failed to start unseal flow")
+                })
+                .map(vault_gate::HandshakeResponse::convert),
+            vault_gate::Outbound::HandleUnsealEncryptedKey(result) => {
+                let proto_result = match result {
+                    Ok(()) => ProtoUnsealResult::Success,
+                    Err(vault_gate::Error::InvalidKey) => ProtoUnsealResult::InvalidKey,
+                    Err(err) => {
+                        warn!(?err, "unseal failed");
+                        return Err(Status::internal("Failed to unseal vault"));
+                    }
+                };
+                Ok(wrap_unseal_response(UnsealResponsePayload::Result(
+                    proto_result.into(),
+                )))
+            }
+            vault_gate::Outbound::HandleBootstrapEncryptedKey(result) => {
+                let proto_result = match result {
+                    Ok(()) => ProtoBootstrapResult::Success,
+                    Err(vault_gate::Error::InvalidKey) => ProtoBootstrapResult::InvalidKey,
+                    Err(vault_gate::Error::AlreadyBootstrapped) => {
+                        ProtoBootstrapResult::AlreadyBootstrapped
+                    }
+                    Err(err) => {
+                        warn!(?err, "bootstrap failed");
+                        return Err(Status::internal("Failed to bootstrap vault"));
+                    }
+                };
+                Ok(wrap_bootstrap_response(proto_result))
+            }
+        }
+    }
+}

server/crates/arbiter-server/src/peers/client/auth.rs

@@ -1,4 +1,4 @@
-use arbiter_crypto::authn::{self, CLIENT_CONTEXT};
+use arbiter_crypto::authn::{self, AuthChallenge, CLIENT_CONTEXT};
 use arbiter_proto::{
     ClientMetadata,
     transport::{Bi, expect_message},
@@ -74,19 +74,14 @@ pub enum Inbound {
 
 #[derive(Debug, Clone)]
 pub enum Outbound {
-    AuthChallenge {
-        pubkey: authn::PublicKey,
-        nonce: i32,
-    },
+    AuthChallenge { challenge: AuthChallenge },
     AuthSuccess,
 }
 
-/// Returns the current nonce and client ID for a registered client.
-/// Returns `None` if the pubkey is not registered.
-async fn get_current_nonce_and_id(
+async fn get_client_id(
     db: &db::DatabasePool,
     pubkey: &authn::PublicKey,
-) -> Result<Option<(i32, i32)>, Error> {
+) -> Result<Option<i32>, Error> {
     let pubkey_bytes = pubkey.to_bytes();
     let mut conn = db.get().await.map_err(|e| {
         error!(error = ?e, "Database pool error");
@@ -94,8 +89,8 @@ async fn get_current_nonce_and_id(
     })?;
     program_client::table
         .filter(program_client::public_key.eq(&pubkey_bytes))
-        .select((program_client::id, program_client::nonce))
-        .first::<(i32, i32)>(&mut conn)
+        .select(program_client::id)
+        .first::<i32>(&mut conn)
         .await
         .optional()
         .map_err(|e| {
@@ -114,7 +109,7 @@ async fn verify_integrity(
         Error::DatabasePoolUnavailable
     })?;
 
-    let (id, nonce) = get_current_nonce_and_id(db, pubkey).await?.ok_or_else(|| {
+    let id = get_client_id(db, pubkey).await?.ok_or_else(|| {
         error!("Client not found during integrity verification");
         Error::DatabaseOperationFailed
     })?;
@@ -124,7 +119,6 @@ async fn verify_integrity(
         vault,
         &ClientCredentials {
             pubkey: pubkey.clone(),
-            nonce,
         },
         id,
     )
@@ -142,53 +136,6 @@ async fn verify_integrity(
     Ok(())
 }
 
-/// Atomically increments the nonce and re-signs the integrity envelope.
-/// Returns the new nonce, which is used as the challenge nonce.
-async fn create_nonce(
-    db: &db::DatabasePool,
-    vault: &ActorRef<Vault>,
-    pubkey: &authn::PublicKey,
-) -> Result<i32, Error> {
-    let pubkey_bytes = pubkey.to_bytes();
-    let pubkey = pubkey.clone();
-
-    let mut conn = db.get().await.map_err(|e| {
-        error!(error = ?e, "Database pool error");
-        Error::DatabasePoolUnavailable
-    })?;
-
-    conn.exclusive_transaction(|conn| {
-        let vault = vault.clone();
-        let pubkey = pubkey.clone();
-        Box::pin(async move {
-            let (id, new_nonce): (i32, i32) = update(program_client::table)
-                .filter(program_client::public_key.eq(&pubkey_bytes))
-                .set(program_client::nonce.eq(program_client::nonce + 1))
-                .returning((program_client::id, program_client::nonce))
-                .get_result(conn)
-                .await?;
-
-            integrity::sign_entity(
-                conn,
-                &vault,
-                &ClientCredentials {
-                    pubkey: pubkey.clone(),
-                    nonce: new_nonce,
-                },
-                id,
-            )
-            .await
-            .map_err(|e| {
-                error!(?e, "Integrity sign failed after nonce update");
-                Error::DatabaseOperationFailed
-            })?;
-
-            Ok(new_nonce)
-        })
-    })
-    .await
-}
-
 async fn approve_new_client(actors: &GlobalActors, profile: ClientProfile) -> Result<(), Error> {
     let result = actors
         .flow_coordinator
@@ -228,8 +175,6 @@ async fn insert_client(
         let vault = vault.clone();
         let pubkey = pubkey.clone();
         Box::pin(async move {
-            const NONCE_START: i32 = 1;
-
             let metadata_id = insert_into(client_metadata::table)
                 .values((
                     client_metadata::name.eq(&metadata.name),
@@ -244,7 +189,6 @@ async fn insert_client(
                 .values((
                     program_client::public_key.eq(pubkey.to_bytes()),
                     program_client::metadata_id.eq(metadata_id),
-                    program_client::nonce.eq(NONCE_START),
                 ))
                 .on_conflict_do_nothing()
                 .returning(program_client::id)
@@ -256,7 +200,6 @@ async fn insert_client(
                 &vault,
                 &ClientCredentials {
                     pubkey: pubkey.clone(),
-                    nonce: NONCE_START,
                 },
                 client_id,
             )
@@ -346,15 +289,14 @@ async fn sync_client_metadata(
 async fn challenge_client<T>(
     transport: &mut T,
     pubkey: authn::PublicKey,
-    nonce: i32,
+    challenge: AuthChallenge,
 ) -> Result<(), Error>
 where
     T: Bi<Inbound, Result<Outbound, Error>> + ?Sized,
 {
     transport
         .send(Ok(Outbound::AuthChallenge {
-            pubkey: pubkey.clone(),
-            nonce,
+            challenge: challenge.clone(),
         }))
         .await
         .map_err(|e| {
@@ -372,7 +314,7 @@ where
         Error::Transport
     })?;
 
-    if !pubkey.verify(nonce, CLIENT_CONTEXT, &signature) {
+    if !pubkey.verify(&challenge, CLIENT_CONTEXT, &signature) {
         error!("Challenge solution verification failed");
         return Err(Error::InvalidChallengeSolution);
     }
@@ -388,8 +330,8 @@ where
         return Err(Error::Transport);
     };
 
-    let client_id = match get_current_nonce_and_id(&props.db, &pubkey).await? {
-        Some((id, _)) => {
+    let client_id = match get_client_id(&props.db, &pubkey).await? {
+        Some(id) => {
             verify_integrity(&props.db, &props.actors.vault, &pubkey).await?;
             id
         }
@@ -407,8 +349,9 @@ where
     };
 
     sync_client_metadata(&props.db, client_id, &metadata).await?;
-    let challenge_nonce = create_nonce(&props.db, &props.actors.vault, &pubkey).await?;
-    challenge_client(transport, pubkey, challenge_nonce).await?;
+
+    let challenge = AuthChallenge::generate(&mut rand::rng());
+    challenge_client(transport, pubkey, challenge).await?;
 
     transport
         .send(Ok(Outbound::AuthSuccess))

server/crates/arbiter-server/src/peers/client/mod.rs

@@ -18,7 +18,6 @@ pub struct ClientProfile {
 
 pub struct ClientCredentials {
     pub pubkey: authn::PublicKey,
-    pub nonce: i32,
 }
 
 impl Integrable for ClientCredentials {
@@ -28,7 +27,6 @@ impl Integrable for ClientCredentials {
 impl Hashable for ClientCredentials {
     fn hash<H: sha2::Digest>(&self, hasher: &mut H) {
         hasher.update(self.pubkey.to_bytes());
-        self.nonce.hash(hasher);
     }
 }
 

server/crates/arbiter-server/src/peers/user_agent/auth/mod.rs

@@ -1,11 +1,12 @@
-use arbiter_crypto::authn;
+use arbiter_crypto::authn::{self, AuthChallenge};
 use arbiter_proto::transport::Bi;
 use tracing::error;
 
 mod state;
 use state::*;
 
-use super::{AuthCredentials, UserAgentConnection};
+use super::Credentials;
+use super::UserAgentConnection;
 
 #[derive(Debug, Clone)]
 pub enum Inbound {
@@ -44,7 +45,7 @@ impl From<diesel::result::Error> for Error {
 
 #[derive(Debug, Clone)]
 pub enum Outbound {
-    AuthChallenge { nonce: i32 },
+    AuthChallenge { challenge: AuthChallenge },
     AuthSuccess,
 }
 
@@ -52,12 +53,11 @@ fn parse_auth_event(payload: Inbound) -> AuthEvents {
     match payload {
         Inbound::AuthChallengeRequest {
             pubkey,
-            bootstrap_token: None,
-        } => AuthEvents::AuthRequest(ChallengeRequest { pubkey }),
-        Inbound::AuthChallengeRequest {
+            bootstrap_token,
+        } => AuthEvents::AuthRequest(ChallengeRequest {
             pubkey,
-            bootstrap_token: Some(token),
-        } => AuthEvents::BootstrapAuthRequest(BootstrapAuthRequest { pubkey, token }),
+            bootstrap_token,
+        }),
         Inbound::AuthChallengeSolution { signature } => {
             AuthEvents::ReceivedSolution(ChallengeSolution {
                 solution: signature,
@@ -69,14 +69,13 @@ fn parse_auth_event(payload: Inbound) -> AuthEvents {
 pub async fn authenticate<T>(
     props: &mut UserAgentConnection,
     transport: &mut T,
-) -> Result<AuthCredentials, Error>
+) -> Result<Credentials, Error>
 where
     T: Bi<Inbound, Result<Outbound, Error>> + Send + ?Sized,
 {
     let mut state = AuthStateMachine::new(AuthContext::new(props, transport));
 
     loop {
-        // `state` holds a mutable reference to `props` so we can't access it directly here
         let Some(payload) = state.context_mut().transport.recv().await else {
             return Err(Error::Transport);
         };

server/crates/arbiter-server/src/peers/user_agent/auth/state.rs

@@ -1,32 +1,26 @@
-use super::super::{AuthCredentials, Credentials, UserAgentConnection};
-use arbiter_crypto::authn::{self, USERAGENT_CONTEXT};
+use super::super::{Credentials, UserAgentConnection};
+use arbiter_crypto::authn::{self, AuthChallenge, USERAGENT_CONTEXT};
 use arbiter_proto::transport::Bi;
-use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl, sqlite::Sqlite, update};
-use diesel_async::{AsyncConnection, RunQueryDsl};
-use kameo::actor::ActorRef;
+use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl};
+use diesel_async::RunQueryDsl;
 use tracing::error;
 
 use super::Error;
-use crate::peers::user_agent::auth::Outbound;
 use crate::{
-    actors::{bootstrap::ConsumeToken, vault::Vault},
-    crypto::integrity,
+    actors::bootstrap::ConsumeToken,
     db::{DatabasePool, schema::useragent_client},
+    peers::user_agent::auth::Outbound,
 };
 
 pub struct ChallengeRequest {
     pub pubkey: authn::PublicKey,
-}
-
-pub struct BootstrapAuthRequest {
-    pub pubkey: authn::PublicKey,
-    pub token: String,
+    pub bootstrap_token: Option<String>,
 }
 
 pub struct ChallengeContext {
-    pub id: i32,
-    pub challenge_nonce: i32,
-    pub key: authn::PublicKey,
+    pub challenge: AuthChallenge,
+    pub pubkey: authn::PublicKey,
+    pub bootstrap_token: Option<String>,
 }
 
 pub struct ChallengeSolution {
@@ -38,116 +32,25 @@ smlang::statemachine!(
     custom_error: true,
     transitions: {
         *Init + AuthRequest(ChallengeRequest) / async prepare_challenge = SentChallenge(ChallengeContext),
-        Init + BootstrapAuthRequest(BootstrapAuthRequest) / async verify_bootstrap_token = AuthOk(AuthCredentials),
-        SentChallenge(ChallengeContext) + ReceivedSolution(ChallengeSolution) / async verify_solution = AuthOk(AuthCredentials),
+        SentChallenge(ChallengeContext) + ReceivedSolution(ChallengeSolution) / async verify_solution = AuthOk(Credentials),
     }
 );
 
-const NONCE_START: i32 = 1;
-
-/// Returns the current nonce, ready to use for the challenge nonce.
-async fn get_current_nonce_and_id(
-    db: &DatabasePool,
-    key: &authn::PublicKey,
-) -> Result<(i32, i32), Error> {
-    let mut db_conn = db.get().await.map_err(|e| {
+async fn get_client_id(db: &DatabasePool, pubkey: &authn::PublicKey) -> Result<Option<i32>, Error> {
+    let mut conn = db.get().await.map_err(|e| {
         error!(error = ?e, "Database pool error");
         Error::internal("Database unavailable")
     })?;
-    db_conn
-        .exclusive_transaction(|conn| {
-            Box::pin(async move {
+
     useragent_client::table
-                    .filter(useragent_client::public_key.eq(key.to_bytes()))
-                    .select((useragent_client::id, useragent_client::nonce))
-                    .first::<(i32, i32)>(conn)
-                    .await
-            })
-        })
+        .filter(useragent_client::public_key.eq(pubkey.to_bytes()))
+        .select(useragent_client::id)
+        .first::<i32>(&mut conn)
         .await
         .optional()
         .map_err(|e| {
             error!(error = ?e, "Database error");
             Error::internal("Database operation failed")
-        })?
-        .ok_or_else(|| {
-            error!(?key, "Public key not found in database");
-            Error::UnregisteredPublicKey
-        })
-}
-
-async fn verify_integrity(
-    db: &DatabasePool,
-    vault: &ActorRef<Vault>,
-    pubkey: &authn::PublicKey,
-) -> Result<(), Error> {
-    let mut db_conn = db.get().await.map_err(|e| {
-        error!(error = ?e, "Database pool error");
-        Error::internal("Database unavailable")
-    })?;
-
-    let (id, nonce) = get_current_nonce_and_id(db, pubkey).await?;
-
-    let _result = integrity::verify_entity(
-        &mut db_conn,
-        vault,
-        &AuthCredentials {
-            creds: Credentials {
-                id,
-                pubkey: pubkey.clone(),
-            },
-            new_nonce: nonce,
-        },
-        id,
-    )
-    .await
-    .map_err(|e| {
-        error!(?e, "Integrity verification failed");
-        Error::internal("Integrity verification failed")
-    })?;
-
-    Ok(())
-}
-
-async fn compute_current_nonce(
-    conn: &mut impl AsyncConnection<Backend = Sqlite>,
-    pubkey: &authn::PublicKey,
-) -> Result<(i32, i32), Error> {
-    update(useragent_client::table)
-        .filter(useragent_client::public_key.eq(pubkey.to_bytes()))
-        .set(useragent_client::nonce.eq(useragent_client::nonce + 1))
-        .returning((useragent_client::id, useragent_client::nonce))
-        .get_result(conn)
-        .await
-        .map_err(|e| {
-            error!(error = ?e, "Database error incrementing nonce");
-            Error::internal("Database operation failed")
-        })
-}
-
-async fn resign_credentials(
-    conn: &mut impl AsyncConnection<Backend = Sqlite>,
-    vault: &ActorRef<Vault>,
-    id: i32,
-    pubkey: &authn::PublicKey,
-    new_nonce: i32,
-) -> Result<(), Error> {
-    integrity::sign_entity(
-        conn,
-        vault,
-        &AuthCredentials {
-            creds: Credentials {
-                id,
-                pubkey: pubkey.clone(),
-            },
-            new_nonce,
-        },
-        id,
-    )
-    .await
-    .map_err(|e| {
-        error!(?e, "Integrity signature update failed");
-        Error::internal("Database error")
         })
 }
 
@@ -159,10 +62,7 @@ async fn register_key(db: &DatabasePool, pubkey: &authn::PublicKey) -> Result<i3
     })?;
 
     let id: i32 = diesel::insert_into(useragent_client::table)
-        .values((
-            useragent_client::public_key.eq(pubkey_bytes),
-            useragent_client::nonce.eq(NONCE_START),
-        ))
+        .values((useragent_client::public_key.eq(pubkey_bytes),))
         .returning(useragent_client::id)
         .get_result(&mut conn)
         .await
@@ -193,38 +93,25 @@ where
 
     async fn prepare_challenge(
         &mut self,
-        ChallengeRequest { pubkey }: ChallengeRequest,
+        ChallengeRequest {
+            pubkey,
+            bootstrap_token,
+        }: ChallengeRequest,
     ) -> Result<ChallengeContext, Self::Error> {
-        let is_signing = integrity::is_signing_available(&self.conn.actors.vault)
-            .await
-            .unwrap_or(false);
-
-        if is_signing {
-            verify_integrity(&self.conn.db, &self.conn.actors.vault, &pubkey).await?;
+        // Verify pubkey is registered (unless bootstrapping)
+        if bootstrap_token.is_none() {
+            let id = get_client_id(&self.conn.db, &pubkey).await?;
+            if id.is_none() {
+                return Err(Error::UnregisteredPublicKey);
+            }
         }
 
-        let vault = self.conn.actors.vault.clone();
-        let mut conn = self.conn.db.get().await.map_err(|e| {
-            error!(error = ?e, "Database pool error");
-            Error::internal("Database unavailable")
-        })?;
-
-        let (id, nonce) = conn
-            .exclusive_transaction(|conn| {
-                let pubkey = pubkey.clone();
-                let vault = vault.clone();
-                Box::pin(async move {
-                    let (id, new_nonce) = compute_current_nonce(conn, &pubkey).await?;
-                    if is_signing {
-                        resign_credentials(conn, &vault, id, &pubkey, new_nonce).await?;
-                    }
-                    Result::<_, Error>::Ok((id, new_nonce))
-                })
-            })
-            .await?;
+        let challenge = AuthChallenge::generate(&mut rand::rng());
 
         self.transport
-            .send(Ok(Outbound::AuthChallenge { nonce }))
+            .send(Ok(Outbound::AuthChallenge {
+                challenge: challenge.clone(),
+            }))
             .await
             .map_err(|e| {
                 error!(?e, "Failed to send auth challenge");
@@ -232,18 +119,41 @@ where
             })?;
 
         Ok(ChallengeContext {
-            id,
-            challenge_nonce: nonce,
-            key: pubkey,
+            challenge,
+            pubkey,
+            bootstrap_token,
         })
     }
 
     #[allow(missing_docs)]
-    #[allow(clippy::result_unit_err)]
-    async fn verify_bootstrap_token(
+    #[allow(clippy::unused_unit)]
+    async fn verify_solution(
         &mut self,
-        BootstrapAuthRequest { pubkey, token }: BootstrapAuthRequest,
-    ) -> Result<AuthCredentials, Self::Error> {
+        ChallengeContext {
+            challenge,
+            pubkey,
+            bootstrap_token,
+        }: &ChallengeContext,
+        ChallengeSolution { solution }: ChallengeSolution,
+    ) -> Result<Credentials, Self::Error> {
+        let signature = authn::Signature::try_from(solution.as_slice()).map_err(|_| {
+            error!("Failed to decode signature in challenge solution");
+            Error::InvalidChallengeSolution
+        })?;
+
+        let valid = pubkey.verify(challenge, USERAGENT_CONTEXT, &signature);
+
+        if !valid {
+            self.transport
+                .send(Err(Error::InvalidChallengeSolution))
+                .await
+                .map_err(|_| Error::Transport)?;
+            return Err(Error::InvalidChallengeSolution);
+        }
+
+        // Resolve client id: bootstrap (consume token + register) or lookup
+        let id = match bootstrap_token {
+            Some(token) => {
                 let token_ok: bool = self
                     .conn
                     .actors
@@ -258,72 +168,29 @@ where
                     })?;
 
                 if !token_ok {
-            error!("Invalid bootstrap token provided");
-            return Err(Error::InvalidBootstrapToken);
-        }
-
-        match token_ok {
-            true => {
-                let id = register_key(&self.conn.db, &pubkey).await?;
-                self.transport
-                    .send(Ok(Outbound::AuthSuccess))
-                    .await
-                    .map_err(|_| Error::Transport)?;
-                Ok(AuthCredentials {
-                    creds: Credentials { id, pubkey },
-                    new_nonce: NONCE_START,
-                })
-            }
-            false => {
                     error!("Invalid bootstrap token provided");
                     self.transport
                         .send(Err(Error::InvalidBootstrapToken))
                         .await
                         .map_err(|_| Error::Transport)?;
-                Err(Error::InvalidBootstrapToken)
-            }
-        }
+                    return Err(Error::InvalidBootstrapToken);
                 }
 
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
-    async fn verify_solution(
-        &mut self,
-        ChallengeContext {
-            id,
-            challenge_nonce,
-            key,
-        }: &ChallengeContext,
-        ChallengeSolution { solution }: ChallengeSolution,
-    ) -> Result<AuthCredentials, Self::Error> {
-        let signature = authn::Signature::try_from(solution.as_slice()).map_err(|_| {
-            error!("Failed to decode signature in challenge solution");
-            Error::InvalidChallengeSolution
-        })?;
+                register_key(&self.conn.db, pubkey).await?
+            }
+            None => get_client_id(&self.conn.db, pubkey)
+                .await?
+                .ok_or(Error::UnregisteredPublicKey)?,
+        };
 
-        let valid = key.verify(*challenge_nonce, USERAGENT_CONTEXT, &signature);
-
-        match valid {
-            true => {
         self.transport
             .send(Ok(Outbound::AuthSuccess))
             .await
             .map_err(|_| Error::Transport)?;
-                Ok(AuthCredentials {
-                    creds: Credentials {
-                        id: *id,
-                        pubkey: key.clone(),
-                    },
-                    new_nonce: *challenge_nonce,
+
+        Ok(Credentials {
+            id,
+            pubkey: pubkey.clone(),
         })
     }
-            false => {
-                self.transport
-                    .send(Err(Error::InvalidChallengeSolution))
-                    .await
-                    .map_err(|_| Error::Transport)?;
-                Err(Error::InvalidChallengeSolution)
-            }
-        }
-    }
 }

server/crates/arbiter-server/src/peers/user_agent/mod.rs

@@ -1,7 +1,10 @@
 use crate::{
-    actors::GlobalActors,
-    crypto::integrity::{self, Integrable},
-    db,
+    actors::{
+        GlobalActors,
+        vault::{GetState, Vault},
+    },
+    crypto::integrity::{self, AttestationStatus, Integrable},
+    db::{self, DatabaseError, DatabasePool},
     peers::client::ClientProfile,
 };
 use arbiter_crypto::authn;
@@ -11,7 +14,7 @@ pub use auth::authenticate;
 use kameo::actor::{ActorRef, Spawn as _};
 pub use session::UserAgentSession;
 use tokio::sync::oneshot;
-use tracing::warn;
+use tracing::{error, warn};
 use vault_gate::VaultGate;
 
 use crate::crypto::integrity::hashing::Hashable;
@@ -20,24 +23,11 @@ pub mod auth;
 pub mod session;
 pub mod vault_gate;
 
-#[derive(Debug, Clone, Hash)]
+#[derive(Debug, Clone)]
 pub struct Credentials {
     pub id: i32,
     pub pubkey: authn::PublicKey,
 }
-impl Hashable for Credentials {
-    fn hash<H: sha2::Digest>(&self, hasher: &mut H) {
-        self.id.hash(hasher);
-        self.pubkey.hash(hasher);
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct AuthCredentials {
-    pub creds: Credentials,
-    // denotes new nonce, not current
-    pub new_nonce: i32,
-}
 
 impl Hashable for authn::PublicKey {
     fn hash<H: sha2::Digest>(&self, hasher: &mut H) {
@@ -45,14 +35,14 @@ impl Hashable for authn::PublicKey {
     }
 }
 
-impl Hashable for AuthCredentials {
+impl Hashable for Credentials {
     fn hash<H: sha2::Digest>(&self, hasher: &mut H) {
-        self.creds.hash(hasher);
-        self.new_nonce.hash(hasher);
+        self.id.hash(hasher);
+        self.pubkey.hash(hasher);
     }
 }
 
-impl Integrable for AuthCredentials {
+impl Integrable for Credentials {
     const KIND: &'static str = "useragent_credentials";
 }
 
@@ -83,6 +73,8 @@ pub enum Error {
     VaultGate(#[from] vault_gate::Error),
     #[error("transport closed unexpectedly")]
     Transport,
+    #[error("database error: {0}")]
+    Database(DatabaseError),
     #[error("internal: {0}")]
     Internal(String),
 }
@@ -93,38 +85,44 @@ impl From<auth::Error> for Error {
     }
 }
 
-pub async fn start<T>(
-    props: &mut UserAgentConnection,
-    mut transport: T,
-    oob_sender: Box<dyn Sender<OutOfBand>>,
-) -> Result<ActorRef<UserAgentSession>, Error>
-where
-    T: Bi<auth::Inbound, Result<auth::Outbound, auth::Error>> + Send,
-    T: Bi<vault_gate::Inbound, Result<vault_gate::Outbound, vault_gate::Error>> + Send,
-{
-    let auth_creds = authenticate(props, &mut transport).await?;
-
-    let creds = if integrity::is_signing_available(&props.actors.vault)
+async fn verify_integrity(
+    db: &DatabasePool,
+    vault: &ActorRef<Vault>,
+    credentials: &Credentials,
+) -> Result<(), Error> {
+    let mut conn = db
+        .get()
         .await
-        .unwrap_or(false)
-    {
-        auth_creds.creds
-    } else {
-        run_vault_gate(props, &mut transport, auth_creds).await?
-    };
+        .map_err(|_| Error::Internal("DB unavailable".into()))?;
+    match integrity::verify_entity(&mut conn, &vault, credentials, credentials.id).await {
+        Ok(AttestationStatus::Attested) => Ok(()),
+        Ok(AttestationStatus::Unavailable) => {
+            Err(Error::Internal("Vault sealed during promotion".into()))
+        }
+        Err(e) => {
+            error!(?e, "Integrity verification failed during unseal promotion");
+            Err(Error::Internal("Integrity check failed".into()))
+        }
+    }
+}
 
-    Ok(UserAgentSession::spawn(UserAgentSession::new(
-        props.clone(),
-        creds,
-        oob_sender,
-    )))
+async fn should_run_gate(vault: &ActorRef<Vault>) -> Result<bool, Error> {
+    let vault_state = vault
+        .ask(GetState {})
+        .await
+        .map_err(|_| Error::Internal("Failed to contact the vault".into()))?;
+
+    Ok(!matches!(
+        vault_state,
+        crate::actors::vault::VaultState::Unsealed
+    ))
 }
 
 async fn run_vault_gate<T>(
     props: &UserAgentConnection,
     transport: &mut T,
-    auth_creds: AuthCredentials,
-) -> Result<Credentials, Error>
+    auth_creds: Credentials,
+) -> Result<(), Error>
 where
     T: Bi<vault_gate::Inbound, Result<vault_gate::Outbound, vault_gate::Error>> + Send + ?Sized,
 {
@@ -173,3 +171,29 @@ where
     gate.kill();
     result
 }
+
+pub async fn start<T>(
+    props: &mut UserAgentConnection,
+    mut transport: T,
+    oob_sender: Box<dyn Sender<OutOfBand>>,
+) -> Result<ActorRef<UserAgentSession>, Error>
+where
+    T: Bi<auth::Inbound, Result<auth::Outbound, auth::Error>> + Send,
+    T: Bi<vault_gate::Inbound, Result<vault_gate::Outbound, vault_gate::Error>> + Send,
+{
+    let creds = authenticate(props, &mut transport).await?;
+
+    // should run vault gate only if sealed / unbootstrapped
+    if should_run_gate(&props.actors.vault).await? {
+        run_vault_gate(props, &mut transport, creds.clone()).await?;
+    }
+
+    // checking the integrity
+    verify_integrity(&props.db, &props.actors.vault, &creds).await?;
+
+    Ok(UserAgentSession::spawn(UserAgentSession::new(
+        props.clone(),
+        creds,
+        oob_sender,
+    )))
+}

server/crates/arbiter-server/src/peers/user_agent/session/handlers.rs

@@ -1,26 +1,21 @@
-use std::sync::Mutex;
 
 use alloy::{consensus::TxEip1559, primitives::Address, signers::Signature};
 use arbiter_crypto::{
     authn,
-    safecell::{SafeCell, SafeCellHandle as _},
+    safecell::SafeCellHandle as _,
 };
-use chacha20poly1305::{AeadInPlace, XChaCha20Poly1305, XNonce, aead::KeyInit};
+use chacha20poly1305::aead::KeyInit;
 use diesel::{ExpressionMethods as _, QueryDsl as _, SelectableHelper};
 use diesel_async::{AsyncConnection, RunQueryDsl};
 use kameo::error::SendError;
 use kameo::messages;
 use kameo::prelude::Context;
-use tracing::{error, info};
-use x25519_dalek::{EphemeralSecret, PublicKey};
+use tracing::error;
 
 use crate::actors::flow_coordinator::client_connect_approval::ClientApprovalAnswer;
-use crate::actors::{
-    evm::{
+use crate::actors::evm::{
         ClientSignTransaction, Generate, ListWallets, SignTransactionError as EvmSignError,
         UseragentCreateGrant, UseragentListGrants,
-    },
-    vault::{self, Bootstrap, TryUnseal},
     };
 use crate::db::models::{
     EvmWalletAccess, NewEvmWalletAccess, ProgramClient, ProgramClientMetadata,

server/crates/arbiter-server/src/peers/user_agent/session/mod.rs

@@ -1,20 +1,18 @@
 use arbiter_crypto::authn;
-use diesel::{ExpressionMethods, QueryDsl};
-use diesel_async::{RunQueryDsl};
-use kameo_actors::message_bus::Register;
 
 use std::{borrow::Cow, collections::HashMap};
 
 use arbiter_proto::transport::Sender;
-use kameo::{Actor, actor::ActorRef, messages, prelude::Message};
+use kameo::{Actor, actor::ActorRef, messages};
 use thiserror::Error;
 use tracing::error;
 
 use crate::{
     actors::{
-        flow_coordinator::{RegisterUserAgent, client_connect_approval::ClientApprovalController},
-        vault::events,
-    }, crypto::integrity, db::schema::useragent_client, peers::{client::ClientProfile, user_agent::{AuthCredentials, Credentials}}
+        flow_coordinator::client_connect_approval::ClientApprovalController,
+        useragent_registry::ConnectUseragent,
+    },
+    peers::{client::ClientProfile, user_agent::Credentials},
 };
 
 use super::{OutOfBand, UserAgentConnection};
@@ -123,17 +121,17 @@ impl Actor for UserAgentSession {
     ) -> Result<Self, Self::Error> {
         args.props
             .actors
-            .flow_coordinator
-            .ask(RegisterUserAgent {
+            .useragent_registry
+            .ask(ConnectUseragent {
                 actor: this.clone(),
             })
             .await
             .map_err(|err| {
                 error!(
                     ?err,
-                    "Failed to register user agent connection with flow coordinator"
+                    "Failed to register user agent connection with user agent registry"
                 );
-                Error::internal("Failed to register user agent connection with flow coordinator")
+                Error::internal("Failed to register user agent connection with user agent registry")
             })?;
         Ok(args)
     }

server/crates/arbiter-server/src/peers/user_agent/vault_gate/mod.rs

@@ -1,22 +1,24 @@
 use arbiter_crypto::safecell::{SafeCell, SafeCellHandle as _};
+use arbiter_proto::transport::Bi;
 use chacha20poly1305::{AeadInPlace, KeyInit as _, XChaCha20Poly1305, XNonce};
 use kameo::{Actor, error::SendError, messages, prelude::Message};
 use kameo_actors::message_bus::Register;
 use tokio::sync::oneshot;
-use tracing::{error, info};
+use tracing::{error, info, warn};
 use x25519_dalek::{EphemeralSecret, PublicKey, SharedSecret};
 
 pub mod state;
 use state::*;
 
-use super::{AuthCredentials, Credentials};
+use super::Credentials;
 use crate::{
     actors::{
         GlobalActors,
-        vault::{self, Bootstrap, TryUnseal, events},
+        vault::{self, Bootstrap, GetState, TryUnseal, VaultState, events},
     },
-    crypto::integrity::{self, AttestationStatus},
+    crypto::integrity::{self},
     db::DatabasePool,
+    peers::user_agent::UserAgentConnection,
 };
 
 #[derive(Debug, thiserror::Error)]
@@ -43,8 +45,8 @@ pub struct HandshakeResponse {
 }
 
 pub struct VaultGate {
-    pub auth_creds: AuthCredentials,
-    pub promotion_tx: Option<oneshot::Sender<Result<Credentials, Error>>>,
+    pub auth_creds: Credentials,
+    pub promotion_tx: Option<oneshot::Sender<Result<(), Error>>>,
     pub state: State,
     pub actors: GlobalActors,
     pub db: DatabasePool,
@@ -52,10 +54,10 @@ pub struct VaultGate {
 
 impl VaultGate {
     pub fn new(
-        auth_creds: AuthCredentials,
+        auth_creds: Credentials,
         actors: GlobalActors,
         db: DatabasePool,
-        promotion_tx: oneshot::Sender<Result<Credentials, Error>>,
+        promotion_tx: oneshot::Sender<Result<(), Error>>,
     ) -> Self {
         Self {
             auth_creds,
@@ -228,6 +230,18 @@ impl VaultGate {
             }
         }
     }
+
+    #[message]
+    pub async fn handle_vault_state(&mut self) -> Result<VaultState, Error> {
+        let answer = self
+            .actors
+            .vault
+            .ask(GetState {})
+            .await
+            .map_err(|_| Error::internal("failed to query vault"))?;
+
+        Ok(answer)
+    }
 }
 
 impl Message<events::Bootstrapped> for VaultGate {
@@ -239,14 +253,23 @@ impl Message<events::Bootstrapped> for VaultGate {
         ctx: &mut kameo::prelude::Context<Self, Self::Reply>,
     ) -> Self::Reply {
         let result = async {
-            let mut conn = self.db.get().await.map_err(|_| Error::internal("DB unavailable"))?;
-            integrity::sign_entity(&mut conn, &self.actors.vault, &self.auth_creds, self.auth_creds.creds.id)
+            let mut conn = self
+                .db
+                .get()
+                .await
+                .map_err(|_| Error::internal("DB unavailable"))?;
+            integrity::sign_entity(
+                &mut conn,
+                &self.actors.vault,
+                &self.auth_creds,
+                self.auth_creds.id,
+            )
             .await
             .map_err(|e| {
                 error!(?e, "Failed to sign integrity envelope on bootstrap");
                 Error::internal("Integrity sign failed")
             })?;
-            Ok(self.auth_creds.creds.clone())
+            Ok(())
         }
         .await;
 
@@ -265,30 +288,8 @@ impl Message<events::Unsealed> for VaultGate {
         _: events::Unsealed,
         ctx: &mut kameo::prelude::Context<Self, Self::Reply>,
     ) -> Self::Reply {
-        let result = async {
-            let mut conn = self.db.get().await.map_err(|_| Error::internal("DB unavailable"))?;
-            match integrity::verify_entity(
-                &mut conn,
-                &self.actors.vault,
-                &self.auth_creds,
-                self.auth_creds.creds.id,
-            )
-            .await
-            {
-                Ok(AttestationStatus::Attested) => Ok(self.auth_creds.creds.clone()),
-                Ok(AttestationStatus::Unavailable) => {
-                    Err(Error::internal("Vault sealed during promotion"))
-                }
-                Err(e) => {
-                    error!(?e, "Integrity verification failed during unseal promotion");
-                    Err(Error::InvalidKey)
-                }
-            }
-        }
-        .await;
-
         if let Some(tx) = self.promotion_tx.take() {
-            let _ = tx.send(result);
+            let _ = tx.send(Ok(()));
         }
         ctx.stop();
     }

server/crates/arbiter-server/src/peers/user_agent/vault_gate/state.rs

@@ -1,6 +1,5 @@
-use std::sync::Mutex;
 
-use x25519_dalek::{EphemeralSecret, PublicKey, SharedSecret};
+use x25519_dalek::{PublicKey, SharedSecret};
 
 pub struct Handshake {
     client_pubkey: PublicKey,

server/crates/arbiter-server/tests/client/auth.rs

@@ -1,5 +1,5 @@
 use arbiter_crypto::{
-    authn::{self, CLIENT_CONTEXT, format_challenge},
+    authn::{self, AuthChallenge, CLIENT_CONTEXT},
     safecell::{SafeCell, SafeCellHandle as _},
 };
 use arbiter_proto::ClientMetadata;
@@ -58,7 +58,6 @@ async fn insert_registered_client(
         &actors.vault,
         &ClientCredentials {
             pubkey: pubkey.into(),
-            nonce: 1,
         },
         client_id,
     )
@@ -66,12 +65,8 @@ async fn insert_registered_client(
     .unwrap();
 }
 
-fn sign_client_challenge(
-    key: &SigningKey<MlDsa87>,
-    nonce: i32,
-    pubkey: &authn::PublicKey,
-) -> authn::Signature {
-    let challenge = format_challenge(nonce, &pubkey.to_bytes());
+fn sign_client_challenge(key: &SigningKey<MlDsa87>, challenge: &AuthChallenge) -> authn::Signature {
+    let challenge = challenge.format();
     key.signing_key()
         .sign_deterministic(&challenge, CLIENT_CONTEXT)
         .unwrap()
@@ -86,10 +81,7 @@ async fn insert_bootstrap_sentinel_useragent(db: &db::DatabasePool) {
         .to_vec();
 
     insert_into(schema::useragent_client::table)
-        .values((
-            schema::useragent_client::public_key.eq(sentinel_key),
-            schema::useragent_client::key_type.eq(1i32),
-        ))
+        .values((schema::useragent_client::public_key.eq(sentinel_key),))
         .execute(&mut conn)
         .await
         .unwrap();
@@ -175,14 +167,14 @@ pub async fn test_challenge_auth() {
         .expect("should receive challenge");
     let challenge = match response {
         Ok(resp) => match resp {
-            auth::Outbound::AuthChallenge { pubkey, nonce } => (pubkey, nonce),
+            auth::Outbound::AuthChallenge { challenge } => challenge,
             other => panic!("Expected AuthChallenge, got {other:?}"),
         },
         Err(err) => panic!("Expected Ok response, got Err({err:?})"),
     };
 
     // Sign the challenge and send solution
-    let signature = sign_client_challenge(&new_key, challenge.1, &challenge.0);
+    let signature = sign_client_challenge(&new_key, &challenge);
 
     test_transport
         .send(auth::Inbound::AuthChallengeSolution { signature })
@@ -230,11 +222,11 @@ pub async fn test_metadata_unchanged_does_not_append_history() {
         .unwrap();
 
     let response = test_transport.recv().await.unwrap().unwrap();
-    let (pubkey, nonce) = match response {
-        auth::Outbound::AuthChallenge { pubkey, nonce } => (pubkey, nonce),
+    let challenge = match response {
+        auth::Outbound::AuthChallenge { challenge } => challenge,
         other => panic!("Expected AuthChallenge, got {other:?}"),
     };
-    let signature = sign_client_challenge(&new_key, nonce, &pubkey);
+    let signature = sign_client_challenge(&new_key, &challenge);
     test_transport
         .send(auth::Inbound::AuthChallengeSolution { signature })
         .await
@@ -292,11 +284,11 @@ pub async fn test_metadata_change_appends_history_and_repoints_binding() {
         .unwrap();
 
     let response = test_transport.recv().await.unwrap().unwrap();
-    let (pubkey, nonce) = match response {
-        auth::Outbound::AuthChallenge { pubkey, nonce } => (pubkey, nonce),
+    let challenge = match response {
+        auth::Outbound::AuthChallenge { challenge } => challenge,
         other => panic!("Expected AuthChallenge, got {other:?}"),
     };
-    let signature = sign_client_challenge(&new_key, nonce, &pubkey);
+    let signature = sign_client_challenge(&new_key, &challenge);
     test_transport
         .send(auth::Inbound::AuthChallengeSolution { signature })
         .await

server/crates/arbiter-server/tests/user_agent/auth.rs

@@ -1,33 +1,145 @@
 use arbiter_crypto::{
-    authn::{self, USERAGENT_CONTEXT, format_challenge},
+    authn::{self, AuthChallenge, USERAGENT_CONTEXT},
     safecell::{SafeCell, SafeCellHandle as _},
 };
 
-use arbiter_proto::transport::{Receiver, Sender};
+use arbiter_proto::transport::{Error as TransportError, Receiver, Sender};
 use arbiter_server::{
     actors::{GlobalActors, bootstrap::GetToken, vault::Bootstrap},
     crypto::integrity,
     db::{self, schema},
-    peers::user_agent::{AuthCredentials, Credentials, UserAgentConnection, auth},
+    peers::user_agent::{self, Credentials, UserAgentConnection, auth, vault_gate},
 };
+use async_trait::async_trait;
 use diesel::{ExpressionMethods as _, QueryDsl, insert_into};
 use diesel_async::RunQueryDsl;
 use ml_dsa::{KeyGen, MlDsa87, SigningKey, signature::Keypair as _};
+use tokio::sync::mpsc;
 
 use super::common::ChannelTransport;
 
 fn sign_useragent_challenge(
     key: &SigningKey<MlDsa87>,
-    nonce: i32,
-    pubkey_bytes: &[u8],
+    challenge: &AuthChallenge,
 ) -> authn::Signature {
-    let challenge = format_challenge(nonce, pubkey_bytes);
+    let challenge = challenge.format();
     key.signing_key()
         .sign_deterministic(&challenge, USERAGENT_CONTEXT)
         .unwrap()
         .into()
 }
 
+fn tamper_challenge(challenge: &AuthChallenge) -> AuthChallenge {
+    let mut challenge = challenge.clone();
+    challenge.nonce[0] ^= 1;
+    challenge
+}
+
+struct NullOobSender;
+
+#[async_trait]
+impl Sender<user_agent::OutOfBand> for NullOobSender {
+    async fn send(&mut self, _item: user_agent::OutOfBand) -> Result<(), TransportError> {
+        Ok(())
+    }
+}
+
+struct StartServerTransport {
+    auth_rx: mpsc::Receiver<auth::Inbound>,
+    auth_tx: mpsc::Sender<Result<auth::Outbound, auth::Error>>,
+    vault_rx: mpsc::Receiver<vault_gate::Inbound>,
+    vault_tx: mpsc::Sender<Result<vault_gate::Outbound, vault_gate::Error>>,
+}
+
+struct StartTestTransport {
+    auth_rx: mpsc::Receiver<Result<auth::Outbound, auth::Error>>,
+    auth_tx: mpsc::Sender<auth::Inbound>,
+}
+
+fn start_transport_pair() -> (StartServerTransport, StartTestTransport) {
+    let (auth_in_tx, auth_in_rx) = mpsc::channel(10);
+    let (auth_out_tx, auth_out_rx) = mpsc::channel(10);
+    let (_vault_in_tx, vault_in_rx) = mpsc::channel(10);
+    let (vault_out_tx, _vault_out_rx) = mpsc::channel(10);
+
+    (
+        StartServerTransport {
+            auth_rx: auth_in_rx,
+            auth_tx: auth_out_tx,
+            vault_rx: vault_in_rx,
+            vault_tx: vault_out_tx,
+        },
+        StartTestTransport {
+            auth_rx: auth_out_rx,
+            auth_tx: auth_in_tx,
+        },
+    )
+}
+
+#[async_trait]
+impl Receiver<auth::Inbound> for StartServerTransport {
+    async fn recv(&mut self) -> Option<auth::Inbound> {
+        self.auth_rx.recv().await
+    }
+}
+
+#[async_trait]
+impl Sender<Result<auth::Outbound, auth::Error>> for StartServerTransport {
+    async fn send(&mut self, item: Result<auth::Outbound, auth::Error>) -> Result<(), TransportError> {
+        self.auth_tx
+            .send(item)
+            .await
+            .map_err(|_| TransportError::ChannelClosed)
+    }
+}
+
+impl arbiter_proto::transport::Bi<auth::Inbound, Result<auth::Outbound, auth::Error>>
+    for StartServerTransport
+{
+}
+
+#[async_trait]
+impl Receiver<vault_gate::Inbound> for StartServerTransport {
+    async fn recv(&mut self) -> Option<vault_gate::Inbound> {
+        self.vault_rx.recv().await
+    }
+}
+
+#[async_trait]
+impl Sender<Result<vault_gate::Outbound, vault_gate::Error>> for StartServerTransport {
+    async fn send(
+        &mut self,
+        item: Result<vault_gate::Outbound, vault_gate::Error>,
+    ) -> Result<(), TransportError> {
+        self.vault_tx
+            .send(item)
+            .await
+            .map_err(|_| TransportError::ChannelClosed)
+    }
+}
+
+impl arbiter_proto::transport::Bi<vault_gate::Inbound, Result<vault_gate::Outbound, vault_gate::Error>>
+    for StartServerTransport
+{
+}
+
+#[async_trait]
+impl Receiver<Result<auth::Outbound, auth::Error>> for StartTestTransport {
+    async fn recv(&mut self) -> Option<Result<auth::Outbound, auth::Error>> {
+        self.auth_rx.recv().await
+    }
+}
+
+#[async_trait]
+impl Sender<auth::Inbound> for StartTestTransport {
+    async fn send(&mut self, item: auth::Inbound) -> Result<(), TransportError> {
+        self.auth_tx
+            .send(item)
+            .await
+            .map_err(|_| TransportError::ChannelClosed)
+    }
+}
+
 #[tokio::test]
 #[test_log::test]
 pub async fn test_bootstrap_token_auth() {
@@ -58,14 +170,29 @@ pub async fn test_bootstrap_token_auth() {
         .await
         .unwrap();
 
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive challenge");
+    let challenge = match response {
+        Ok(auth::Outbound::AuthChallenge { challenge }) => challenge,
+        other => panic!("Expected AuthChallenge, got {other:?}"),
+    };
+
+    let signature = sign_useragent_challenge(&new_key, &challenge);
+
+    test_transport
+        .send(auth::Inbound::AuthChallengeSolution {
+            signature: signature.to_bytes(),
+        })
+        .await
+        .unwrap();
+
     let response = test_transport
         .recv()
         .await
         .expect("should receive auth result");
-    match response {
-        Ok(auth::Outbound::AuthSuccess) => {}
-        other => panic!("Expected AuthSuccess, got {other:?}"),
-    }
+    assert!(matches!(response, Ok(auth::Outbound::AuthSuccess)));
 
     task.await.unwrap().unwrap();
 
@@ -100,6 +227,23 @@ pub async fn test_bootstrap_invalid_token_auth() {
         .await
         .unwrap();
 
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive challenge");
+    let challenge = match response {
+        Ok(auth::Outbound::AuthChallenge { challenge }) => challenge,
+        other => panic!("Expected AuthChallenge, got {other:?}"),
+    };
+
+    let signature = sign_useragent_challenge(&new_key, &challenge);
+    test_transport
+        .send(auth::Inbound::AuthChallengeSolution {
+            signature: signature.to_bytes(),
+        })
+        .await
+        .unwrap();
+
     assert!(matches!(
         task.await.unwrap(),
         Err(auth::Error::InvalidBootstrapToken)
@@ -133,10 +277,7 @@ pub async fn test_challenge_auth() {
     {
         let mut conn = db.get().await.unwrap();
         let id: i32 = insert_into(schema::useragent_client::table)
-            .values((
-                schema::useragent_client::public_key.eq(pubkey_bytes.clone()),
-                schema::useragent_client::key_type.eq(1i32),
-            ))
+            .values((schema::useragent_client::public_key.eq(pubkey_bytes.clone()),))
             .returning(schema::useragent_client::id)
             .get_result(&mut conn)
             .await
@@ -144,13 +285,10 @@ pub async fn test_challenge_auth() {
         integrity::sign_entity(
             &mut conn,
             &actors.vault,
-            &AuthCredentials {
-                creds: Credentials {
+            &Credentials {
                 id,
                 pubkey: new_key.verifying_key().into(),
             },
-                new_nonce: 1,
-            },
             id,
         )
         .await
@@ -178,13 +316,13 @@ pub async fn test_challenge_auth() {
         .expect("should receive challenge");
     let challenge = match response {
         Ok(resp) => match resp {
-            auth::Outbound::AuthChallenge { nonce } => nonce,
+            auth::Outbound::AuthChallenge { challenge } => challenge,
             other => panic!("Expected AuthChallenge, got {other:?}"),
         },
         Err(err) => panic!("Expected Ok response, got Err({err:?})"),
     };
 
-    let signature = sign_useragent_challenge(&new_key, challenge, &pubkey_bytes);
+    let signature = sign_useragent_challenge(&new_key, &challenge);
 
     test_transport
         .send(auth::Inbound::AuthChallengeSolution {
@@ -225,20 +363,17 @@ pub async fn test_challenge_auth_rejects_integrity_tag_mismatch_when_unsealed()
     {
         let mut conn = db.get().await.unwrap();
         insert_into(schema::useragent_client::table)
-            .values((
-                schema::useragent_client::public_key.eq(pubkey_bytes.clone()),
-                schema::useragent_client::key_type.eq(1i32),
-            ))
+            .values((schema::useragent_client::public_key.eq(pubkey_bytes.clone()),))
             .execute(&mut conn)
             .await
             .unwrap();
     }
 
-    let (mut server_transport, mut test_transport) = ChannelTransport::new();
+    let (server_transport, mut test_transport) = start_transport_pair();
     let db_for_task = db.clone();
     let task = tokio::spawn(async move {
         let mut props = UserAgentConnection::new(db_for_task, actors);
-        auth::authenticate(&mut props, &mut server_transport).await
+        user_agent::start(&mut props, server_transport, Box::new(NullOobSender)).await
     });
 
     test_transport
@@ -249,9 +384,36 @@ pub async fn test_challenge_auth_rejects_integrity_tag_mismatch_when_unsealed()
         .await
         .unwrap();
 
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive challenge");
+    let challenge = match response {
+        Ok(resp) => match resp {
+            auth::Outbound::AuthChallenge { challenge } => challenge,
+            other => panic!("Expected AuthChallenge, got {other:?}"),
+        },
+        Err(err) => panic!("Expected Ok response, got Err({err:?})"),
+    };
+
+    let signature = sign_useragent_challenge(&new_key, &challenge);
+
+    test_transport
+        .send(auth::Inbound::AuthChallengeSolution {
+            signature: signature.to_bytes(),
+        })
+        .await
+        .unwrap();
+
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive auth result");
+    assert!(matches!(response, Ok(auth::Outbound::AuthSuccess)));
+
     assert!(matches!(
         task.await.unwrap(),
-        Err(auth::Error::Internal { .. })
+        Err(user_agent::Error::Internal(_))
     ));
 }
 
@@ -274,10 +436,7 @@ pub async fn test_challenge_auth_rejects_invalid_signature() {
     {
         let mut conn = db.get().await.unwrap();
         let id: i32 = insert_into(schema::useragent_client::table)
-            .values((
-                schema::useragent_client::public_key.eq(pubkey_bytes.clone()),
-                schema::useragent_client::key_type.eq(1i32),
-            ))
+            .values((schema::useragent_client::public_key.eq(pubkey_bytes.clone()),))
             .returning(schema::useragent_client::id)
             .get_result(&mut conn)
             .await
@@ -285,13 +444,10 @@ pub async fn test_challenge_auth_rejects_invalid_signature() {
         integrity::sign_entity(
             &mut conn,
             &actors.vault,
-            &AuthCredentials {
-                creds: Credentials {
+            &Credentials {
                 id,
                 pubkey: new_key.verifying_key().into(),
             },
-                new_nonce: 1,
-            },
             id,
         )
         .await
@@ -319,13 +475,13 @@ pub async fn test_challenge_auth_rejects_invalid_signature() {
         .expect("should receive challenge");
     let challenge = match response {
         Ok(resp) => match resp {
-            auth::Outbound::AuthChallenge { nonce } => nonce,
+            auth::Outbound::AuthChallenge { challenge } => challenge,
             other => panic!("Expected AuthChallenge, got {other:?}"),
         },
         Err(err) => panic!("Expected Ok response, got Err({err:?})"),
     };
 
-    let signature = sign_useragent_challenge(&new_key, challenge + 1, &pubkey_bytes);
+    let signature = sign_useragent_challenge(&new_key, &tamper_challenge(&challenge));
 
     test_transport
         .send(auth::Inbound::AuthChallengeSolution {

server/crates/arbiter-server/tests/user_agent/unseal.rs

@@ -9,8 +9,10 @@ use arbiter_server::{
     },
     db,
     peers::user_agent::{
-        AuthCredentials, Credentials,
-        vault_gate::{Error as VaultGateError, HandleHandshake, HandleUnsealEncryptedKey, VaultGate},
+        Credentials,
+        vault_gate::{
+            Error as VaultGateError, HandleHandshake, HandleUnsealEncryptedKey, VaultGate,
+        },
     },
 };
 
@@ -21,7 +23,11 @@ use x25519_dalek::{EphemeralSecret, PublicKey};
 
 async fn setup_sealed_gate(
     seal_key: &[u8],
-) -> (db::DatabasePool, kameo::actor::ActorRef<VaultGate>, oneshot::Receiver<Result<Credentials, VaultGateError>>) {
+) -> (
+    db::DatabasePool,
+    kameo::actor::ActorRef<VaultGate>,
+    oneshot::Receiver<Result<(), VaultGateError>>,
+) {
     let db = db::create_test_pool().await;
     let actors = GlobalActors::spawn(db.clone()).await.unwrap();
 
@@ -36,10 +42,7 @@ async fn setup_sealed_gate(
 
     let (promotion_tx, promotion_rx) = oneshot::channel();
     let pubkey = authn::SigningKey::generate().public_key();
-    let auth_creds = AuthCredentials {
-        creds: Credentials { id: 1, pubkey },
-        new_nonce: 1,
-    };
+    let auth_creds = Credentials { id: 1, pubkey };
     let gate = VaultGate::spawn(VaultGate::new(auth_creds, actors, db.clone(), promotion_tx));
 
     (db, gate, promotion_rx)

server/crates/arbiter-server/tests/vault/lifecycle.rs

@@ -87,7 +87,7 @@ async fn test_new_restores_sealed_state() {
         .await
         .unwrap();
     let err = actor2.decrypt(1).await.unwrap_err();
-    assert!(matches!(err, Error::NotBootstrapped));
+    assert!(matches!(err, Error::Sealed));
 }
 
 #[tokio::test]

useragent/lib/features/connection/auth.dart

@@ -7,6 +7,7 @@ import 'package:arbiter/features/identity/pk_manager.dart';
 import 'package:arbiter/proto/arbiter.pbgrpc.dart';
 import 'package:arbiter/proto/user_agent/auth.pb.dart' as ua_auth;
 import 'package:arbiter/proto/user_agent.pb.dart';
+import 'package:arbiter/src/rust/api.dart';
 import 'package:grpc/grpc.dart';
 import 'package:mtcore/markettakers.dart';
 
@@ -92,7 +93,10 @@ Future<Connection> connectAndAuthorize(
       );
     }
 
-    final challenge = _formatChallenge(authResponse.challenge, pubkey);
+    final challenge = await formatChallenge(
+      random: authResponse.challenge.random,
+      timestamp: authResponse.challenge.timestampNanos.toInt(),
+    );
     talker.info(
       'Received auth challenge, signing with key ${base64Encode(pubkey)}',
     );
@@ -164,9 +168,3 @@ Future<Connection> _connect(StoredServerInfo serverInfo) async {
 
   return Connection(channel: channel, tx: tx, rx: rx);
 }
-
-List<int> _formatChallenge(ua_auth.AuthChallenge challenge, List<int> pubkey) {
-  final encodedPubkey = base64Encode(pubkey);
-  final payload = "${challenge.nonce}:$encodedPubkey";
-  return utf8.encode(payload);
-}

useragent/lib/proto/client/auth.pb.dart

@@ -12,6 +12,7 @@
 
 import 'dart:core' as $core;
 
+import 'package:fixnum/fixnum.dart' as $fixnum;
 import 'package:protobuf/protobuf.dart' as $pb;
 
 import '../shared/client.pb.dart' as $0;
@@ -94,12 +95,12 @@ class AuthChallengeRequest extends $pb.GeneratedMessage {
 
 class AuthChallenge extends $pb.GeneratedMessage {
   factory AuthChallenge({
-    $core.List<$core.int>? pubkey,
-    $core.int? nonce,
+    $fixnum.Int64? timestampNanos,
+    $core.List<$core.int>? random,
   }) {
     final result = create();
-    if (pubkey != null) result.pubkey = pubkey;
-    if (nonce != null) result.nonce = nonce;
+    if (timestampNanos != null) result.timestampNanos = timestampNanos;
+    if (random != null) result.random = random;
     return result;
   }
 
@@ -117,9 +118,11 @@ class AuthChallenge extends $pb.GeneratedMessage {
       package:
           const $pb.PackageName(_omitMessageNames ? '' : 'arbiter.client.auth'),
       createEmptyInstance: create)
+    ..a<$fixnum.Int64>(
+        1, _omitFieldNames ? '' : 'timestampNanos', $pb.PbFieldType.OU6,
+        defaultOrMaker: $fixnum.Int64.ZERO)
     ..a<$core.List<$core.int>>(
-        1, _omitFieldNames ? '' : 'pubkey', $pb.PbFieldType.OY)
-    ..aI(2, _omitFieldNames ? '' : 'nonce')
+        2, _omitFieldNames ? '' : 'random', $pb.PbFieldType.OY)
     ..hasRequiredFields = false;
 
   @$core.Deprecated('See https://github.com/google/protobuf.dart/issues/998.')
@@ -142,22 +145,22 @@ class AuthChallenge extends $pb.GeneratedMessage {
   static AuthChallenge? _defaultInstance;
 
   @$pb.TagNumber(1)
-  $core.List<$core.int> get pubkey => $_getN(0);
+  $fixnum.Int64 get timestampNanos => $_getI64(0);
   @$pb.TagNumber(1)
-  set pubkey($core.List<$core.int> value) => $_setBytes(0, value);
+  set timestampNanos($fixnum.Int64 value) => $_setInt64(0, value);
   @$pb.TagNumber(1)
-  $core.bool hasPubkey() => $_has(0);
+  $core.bool hasTimestampNanos() => $_has(0);
   @$pb.TagNumber(1)
-  void clearPubkey() => $_clearField(1);
+  void clearTimestampNanos() => $_clearField(1);
 
   @$pb.TagNumber(2)
-  $core.int get nonce => $_getIZ(1);
+  $core.List<$core.int> get random => $_getN(1);
   @$pb.TagNumber(2)
-  set nonce($core.int value) => $_setSignedInt32(1, value);
+  set random($core.List<$core.int> value) => $_setBytes(1, value);
   @$pb.TagNumber(2)
-  $core.bool hasNonce() => $_has(1);
+  $core.bool hasRandom() => $_has(1);
   @$pb.TagNumber(2)
-  void clearNonce() => $_clearField(2);
+  void clearRandom() => $_clearField(2);
 }
 
 class AuthChallengeSolution extends $pb.GeneratedMessage {

useragent/lib/proto/client/auth.pbjson.dart

@@ -62,15 +62,15 @@ final $typed_data.Uint8List authChallengeRequestDescriptor = $convert.base64Deco
 const AuthChallenge$json = {
   '1': 'AuthChallenge',
   '2': [
-    {'1': 'pubkey', '3': 1, '4': 1, '5': 12, '10': 'pubkey'},
-    {'1': 'nonce', '3': 2, '4': 1, '5': 5, '10': 'nonce'},
+    {'1': 'timestamp_nanos', '3': 1, '4': 1, '5': 4, '10': 'timestampNanos'},
+    {'1': 'random', '3': 2, '4': 1, '5': 12, '10': 'random'},
   ],
 };
 
 /// Descriptor for `AuthChallenge`. Decode as a `google.protobuf.DescriptorProto`.
 final $typed_data.Uint8List authChallengeDescriptor = $convert.base64Decode(
-    'Cg1BdXRoQ2hhbGxlbmdlEhYKBnB1YmtleRgBIAEoDFIGcHVia2V5EhQKBW5vbmNlGAIgASgFUg'
-    'Vub25jZQ==');
+    'Cg1BdXRoQ2hhbGxlbmdlEicKD3RpbWVzdGFtcF9uYW5vcxgBIAEoBFIOdGltZXN0YW1wTmFub3'
+    'MSFgoGcmFuZG9tGAIgASgMUgZyYW5kb20=');
 
 @$core.Deprecated('Use authChallengeSolutionDescriptor instead')
 const AuthChallengeSolution$json = {

useragent/lib/proto/user_agent/auth.pb.dart

@@ -12,6 +12,7 @@
 
 import 'dart:core' as $core;
 
+import 'package:fixnum/fixnum.dart' as $fixnum;
 import 'package:protobuf/protobuf.dart' as $pb;
 
 import 'auth.pbenum.dart';
@@ -90,10 +91,12 @@ class AuthChallengeRequest extends $pb.GeneratedMessage {
 
 class AuthChallenge extends $pb.GeneratedMessage {
   factory AuthChallenge({
-    $core.int? nonce,
+    $fixnum.Int64? timestampNanos,
+    $core.List<$core.int>? random,
   }) {
     final result = create();
-    if (nonce != null) result.nonce = nonce;
+    if (timestampNanos != null) result.timestampNanos = timestampNanos;
+    if (random != null) result.random = random;
     return result;
   }
 
@@ -111,7 +114,11 @@ class AuthChallenge extends $pb.GeneratedMessage {
       package: const $pb.PackageName(
           _omitMessageNames ? '' : 'arbiter.user_agent.auth'),
       createEmptyInstance: create)
-    ..aI(1, _omitFieldNames ? '' : 'nonce')
+    ..a<$fixnum.Int64>(
+        1, _omitFieldNames ? '' : 'timestampNanos', $pb.PbFieldType.OU6,
+        defaultOrMaker: $fixnum.Int64.ZERO)
+    ..a<$core.List<$core.int>>(
+        2, _omitFieldNames ? '' : 'random', $pb.PbFieldType.OY)
     ..hasRequiredFields = false;
 
   @$core.Deprecated('See https://github.com/google/protobuf.dart/issues/998.')
@@ -134,13 +141,22 @@ class AuthChallenge extends $pb.GeneratedMessage {
   static AuthChallenge? _defaultInstance;
 
   @$pb.TagNumber(1)
-  $core.int get nonce => $_getIZ(0);
+  $fixnum.Int64 get timestampNanos => $_getI64(0);
   @$pb.TagNumber(1)
-  set nonce($core.int value) => $_setSignedInt32(0, value);
+  set timestampNanos($fixnum.Int64 value) => $_setInt64(0, value);
   @$pb.TagNumber(1)
-  $core.bool hasNonce() => $_has(0);
+  $core.bool hasTimestampNanos() => $_has(0);
   @$pb.TagNumber(1)
-  void clearNonce() => $_clearField(1);
+  void clearTimestampNanos() => $_clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.List<$core.int> get random => $_getN(1);
+  @$pb.TagNumber(2)
+  set random($core.List<$core.int> value) => $_setBytes(1, value);
+  @$pb.TagNumber(2)
+  $core.bool hasRandom() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearRandom() => $_clearField(2);
 }
 
 class AuthChallengeSolution extends $pb.GeneratedMessage {

useragent/lib/proto/user_agent/auth.pbjson.dart

@@ -67,13 +67,15 @@ final $typed_data.Uint8List authChallengeRequestDescriptor = $convert.base64Deco
 const AuthChallenge$json = {
   '1': 'AuthChallenge',
   '2': [
-    {'1': 'nonce', '3': 1, '4': 1, '5': 5, '10': 'nonce'},
+    {'1': 'timestamp_nanos', '3': 1, '4': 1, '5': 4, '10': 'timestampNanos'},
+    {'1': 'random', '3': 2, '4': 1, '5': 12, '10': 'random'},
   ],
 };
 
 /// Descriptor for `AuthChallenge`. Decode as a `google.protobuf.DescriptorProto`.
-final $typed_data.Uint8List authChallengeDescriptor = $convert
-    .base64Decode('Cg1BdXRoQ2hhbGxlbmdlEhQKBW5vbmNlGAEgASgFUgVub25jZQ==');
+final $typed_data.Uint8List authChallengeDescriptor = $convert.base64Decode(
+    'Cg1BdXRoQ2hhbGxlbmdlEicKD3RpbWVzdGFtcF9uYW5vcxgBIAEoBFIOdGltZXN0YW1wTmFub3'
+    'MSFgoGcmFuZG9tGAIgASgMUgZyYW5kb20=');
 
 @$core.Deprecated('Use authChallengeSolutionDescriptor instead')
 const AuthChallengeSolution$json = {

useragent/lib/src/rust/api.dart

@@ -6,6 +6,14 @@
 import 'frb_generated.dart';
 import 'package:flutter_rust_bridge/flutter_rust_bridge_for_generated.dart';
 
+Future<Uint8List> formatChallenge({
+  required List<int> random,
+  required PlatformInt64 timestamp,
+}) => RustLib.instance.api.crateApiFormatChallenge(
+  random: random,
+  timestamp: timestamp,
+);
+
 // Rust type: RustOpaqueMoi<flutter_rust_bridge::for_generated::RustAutoOpaqueInner<MldsaKey>>
 abstract class MldsaKey implements RustOpaqueInterface {
   static Future<MldsaKey> fromBytes({required List<int> bytes}) =>

useragent/lib/src/rust/frb_generated.dart

@@ -64,7 +64,7 @@ class RustLib extends BaseEntrypoint<RustLibApi, RustLibApiImpl, RustLibWire> {
   String get codegenVersion => '2.12.0';
 
   @override
-  int get rustContentHash => -437661335;
+  int get rustContentHash => 1247923898;
 
   static const kDefaultExternalLibraryLoaderConfig =
       ExternalLibraryLoaderConfig(
@@ -89,6 +89,11 @@ abstract class RustLibApi extends BaseApi {
 
   Future<Uint8List> crateApiMldsaKeyToBytes({required MldsaKey that});
 
+  Future<Uint8List> crateApiFormatChallenge({
+    required List<int> random,
+    required PlatformInt64 timestamp,
+  });
+
   RustArcIncrementStrongCountFnType
   get rust_arc_increment_strong_count_MldsaKey;
 
@@ -267,6 +272,40 @@ class RustLibApiImpl extends RustLibApiImplPlatform implements RustLibApi {
   TaskConstMeta get kCrateApiMldsaKeyToBytesConstMeta =>
       const TaskConstMeta(debugName: "MldsaKey_to_bytes", argNames: ["that"]);
 
+  @override
+  Future<Uint8List> crateApiFormatChallenge({
+    required List<int> random,
+    required PlatformInt64 timestamp,
+  }) {
+    return handler.executeNormal(
+      NormalTask(
+        callFfi: (port_) {
+          final serializer = SseSerializer(generalizedFrbRustBinding);
+          sse_encode_list_prim_u_8_loose(random, serializer);
+          sse_encode_i_64(timestamp, serializer);
+          pdeCallFfi(
+            generalizedFrbRustBinding,
+            serializer,
+            funcId: 6,
+            port: port_,
+          );
+        },
+        codec: SseCodec(
+          decodeSuccessData: sse_decode_list_prim_u_8_strict,
+          decodeErrorData: sse_decode_String,
+        ),
+        constMeta: kCrateApiFormatChallengeConstMeta,
+        argValues: [random, timestamp],
+        apiImpl: this,
+      ),
+    );
+  }
+
+  TaskConstMeta get kCrateApiFormatChallengeConstMeta => const TaskConstMeta(
+    debugName: "format_challenge",
+    argNames: ["random", "timestamp"],
+  );
+
   RustArcIncrementStrongCountFnType
   get rust_arc_increment_strong_count_MldsaKey => wire
       .rust_arc_increment_strong_count_RustOpaque_flutter_rust_bridgefor_generatedRustAutoOpaqueInnerMldsaKey;
@@ -314,6 +353,12 @@ class RustLibApiImpl extends RustLibApiImplPlatform implements RustLibApi {
     return raw as String;
   }
 
+  @protected
+  PlatformInt64 dco_decode_i_64(dynamic raw) {
+    // Codec=Dco (DartCObject based), see doc to use other codecs
+    return dcoDecodeI64(raw);
+  }
+
   @protected
   List<int> dco_decode_list_prim_u_8_loose(dynamic raw) {
     // Codec=Dco (DartCObject based), see doc to use other codecs
@@ -394,6 +439,12 @@ class RustLibApiImpl extends RustLibApiImplPlatform implements RustLibApi {
     return utf8.decoder.convert(inner);
   }
 
+  @protected
+  PlatformInt64 sse_decode_i_64(SseDeserializer deserializer) {
+    // Codec=Sse (Serialization based), see doc to use other codecs
+    return deserializer.buffer.getPlatformInt64();
+  }
+
   @protected
   List<int> sse_decode_list_prim_u_8_loose(SseDeserializer deserializer) {
     // Codec=Sse (Serialization based), see doc to use other codecs
@@ -491,6 +542,12 @@ class RustLibApiImpl extends RustLibApiImplPlatform implements RustLibApi {
     sse_encode_list_prim_u_8_strict(utf8.encoder.convert(self), serializer);
   }
 
+  @protected
+  void sse_encode_i_64(PlatformInt64 self, SseSerializer serializer) {
+    // Codec=Sse (Serialization based), see doc to use other codecs
+    serializer.buffer.putPlatformInt64(self);
+  }
+
   @protected
   void sse_encode_list_prim_u_8_loose(
     List<int> self,

useragent/lib/src/rust/frb_generated.io.dart

@@ -46,6 +46,9 @@ abstract class RustLibApiImplPlatform extends BaseApiImpl<RustLibWire> {
   @protected
   String dco_decode_String(dynamic raw);
 
+  @protected
+  PlatformInt64 dco_decode_i_64(dynamic raw);
+
   @protected
   List<int> dco_decode_list_prim_u_8_loose(dynamic raw);
 
@@ -85,6 +88,9 @@ abstract class RustLibApiImplPlatform extends BaseApiImpl<RustLibWire> {
   @protected
   String sse_decode_String(SseDeserializer deserializer);
 
+  @protected
+  PlatformInt64 sse_decode_i_64(SseDeserializer deserializer);
+
   @protected
   List<int> sse_decode_list_prim_u_8_loose(SseDeserializer deserializer);
 
@@ -136,6 +142,9 @@ abstract class RustLibApiImplPlatform extends BaseApiImpl<RustLibWire> {
   @protected
   void sse_encode_String(String self, SseSerializer serializer);
 
+  @protected
+  void sse_encode_i_64(PlatformInt64 self, SseSerializer serializer);
+
   @protected
   void sse_encode_list_prim_u_8_loose(List<int> self, SseSerializer serializer);
 

useragent/lib/src/rust/frb_generated.web.dart

@@ -48,6 +48,9 @@ abstract class RustLibApiImplPlatform extends BaseApiImpl<RustLibWire> {
   @protected
   String dco_decode_String(dynamic raw);
 
+  @protected
+  PlatformInt64 dco_decode_i_64(dynamic raw);
+
   @protected
   List<int> dco_decode_list_prim_u_8_loose(dynamic raw);
 
@@ -87,6 +90,9 @@ abstract class RustLibApiImplPlatform extends BaseApiImpl<RustLibWire> {
   @protected
   String sse_decode_String(SseDeserializer deserializer);
 
+  @protected
+  PlatformInt64 sse_decode_i_64(SseDeserializer deserializer);
+
   @protected
   List<int> sse_decode_list_prim_u_8_loose(SseDeserializer deserializer);
 
@@ -138,6 +144,9 @@ abstract class RustLibApiImplPlatform extends BaseApiImpl<RustLibWire> {
   @protected
   void sse_encode_String(String self, SseSerializer serializer);
 
+  @protected
+  void sse_encode_i_64(PlatformInt64 self, SseSerializer serializer);
+
   @protected
   void sse_encode_list_prim_u_8_loose(List<int> self, SseSerializer serializer);
 

useragent/mise.toml

@@ -0,0 +1,4 @@
+[tasks.codegen]
+run = '''
+  flutter_rust_bridge_codegen generate 
+'''

useragent/rust/Cargo.lock

@@ -232,10 +232,11 @@ checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
 name = "arbiter-crypto"
 version = "0.1.0"
 dependencies = [
- "base64",
+ "chrono",
  "memsafe",
  "ml-dsa",
  "rand",
+ "x-wing",
 ]
 
 [[package]]
@@ -486,12 +487,6 @@ dependencies = [
  "rustc-demangle",
 ]
 
-[[package]]
-name = "base64"
-version = "0.22.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
-
 [[package]]
 name = "base64ct"
 version = "1.8.3"
@@ -713,10 +708,24 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6f8d983286843e49675a4b7a2d174efe136dc93a18d69130dd18198a6c167601"
 dependencies = [
  "cfg-if",
- "cpufeatures",
+ "cpufeatures 0.3.0",
  "rand_core",
 ]
 
+[[package]]
+name = "chrono"
+version = "0.4.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c673075a2e0e5f4a1dde27ce9dee1ea4558c7ffe648f576438a20ca1d2acc4b0"
+dependencies = [
+ "iana-time-zone",
+ "js-sys",
+ "num-traits",
+ "serde",
+ "wasm-bindgen",
+ "windows-link",
+]
+
 [[package]]
 name = "clipboard-win"
 version = "5.4.1"
@@ -837,6 +846,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59ed5838eebb26a2bb2e58f6d5b5316989ae9d08bab10e0e6d103e656d1b0280"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "cpufeatures"
 version = "0.3.0"
@@ -884,6 +902,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77727bb15fa921304124b128af125e7e3b968275d1b108b379190264f4423710"
 dependencies = [
  "hybrid-array",
+ "rand_core",
 ]
 
 [[package]]
@@ -901,6 +920,32 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f27ae1dd37df86211c42e150270f82743308803d90a6f6e6651cd730d5e1732f"
 
+[[package]]
+name = "curve25519-dalek"
+version = "5.0.0-pre.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "335f1947f241137a14106b6f5acc5918a5ede29c9d71d3f2cb1678d5075d9fc3"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.2.17",
+ "curve25519-dalek-derive",
+ "fiat-crypto",
+ "rustc_version",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "curve25519-dalek-derive"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f46882e17999c6cc590af592290432be3bce0428cb0d5f8b6715e4dc7b383eb3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "dart-sys"
 version = "4.1.5"
@@ -1314,6 +1359,12 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "fiat-crypto"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64cd1e32ddd350061ae6edb1b082d7c54915b5c672c389143b9a63403a109f24"
+
 [[package]]
 name = "flate2"
 version = "1.1.9"
@@ -1773,10 +1824,35 @@ version = "0.4.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3944cf8cf766b40e2a1a333ee5e9b563f854d5fa49d6a8ca2764e97c6eddb214"
 dependencies = [
+ "ctutils",
  "typenum",
  "zeroize",
 ]
 
+[[package]]
+name = "iana-time-zone"
+version = "0.1.65"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e31bc9ad994ba00e440a8aa5c9ef0ec67d5cb5e5cb0cc7f8b744a35b389cc470"
+dependencies = [
+ "android_system_properties",
+ "core-foundation-sys",
+ "iana-time-zone-haiku",
+ "js-sys",
+ "log",
+ "wasm-bindgen",
+ "windows-core",
+]
+
+[[package]]
+name = "iana-time-zone-haiku"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f31827a206f56af32e590ba56d5d2d085f558508192593743f16b2306495269f"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "icu_collections"
 version = "2.2.0"
@@ -2005,7 +2081,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9e24a010dd405bd7ed803e5253182815b41bf2e6a80cc3bfc066658e03a198aa"
 dependencies = [
  "cfg-if",
- "cpufeatures",
+ "cpufeatures 0.3.0",
+]
+
+[[package]]
+name = "kem"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "01737161ba802849cfd486b5bd209d38ba4943494c249a8126005170c7621edd"
+dependencies = [
+ "crypto-common 0.2.1",
+ "rand_core",
 ]
 
 [[package]]
@@ -2207,12 +2293,27 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "ml-kem"
+version = "0.3.0-rc.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04437cb1a66c0b78740927b76cc61f218344b9f6ef3dd430e283274a718ef0e9"
+dependencies = [
+ "hybrid-array",
+ "kem",
+ "module-lattice",
+ "rand_core",
+ "sha3",
+ "zeroize",
+]
+
 [[package]]
 name = "module-lattice"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "164eb3faeaecbd14b0b2a917c1b4d0c035097a9c559b0bed85c2cdd032bc8faa"
 dependencies = [
+ "ctutils",
  "hybrid-array",
  "num-traits",
  "zeroize",
@@ -3488,6 +3589,12 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6637bab7722d379c8b41ba849228d680cc12d0a45ba1fa2b48f2a30577a06731"
 
+[[package]]
+name = "subtle"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
+
 [[package]]
 name = "syn"
 version = "2.0.117"
@@ -4761,6 +4868,20 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1ffae5123b2d3fc086436f8834ae3ab053a283cfac8fe0a0b8eaae044768a4c4"
 
+[[package]]
+name = "x-wing"
+version = "0.1.0-rc.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e17d0d5f4d1f26b9b9e7477af1d3bef960e1d1fb64edab7912fde472a8a8432e"
+dependencies = [
+ "kem",
+ "ml-kem",
+ "rand_core",
+ "sha3",
+ "x25519-dalek",
+ "zeroize",
+]
+
 [[package]]
 name = "x11-dl"
 version = "2.21.0"
@@ -4793,6 +4914,17 @@ version = "0.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ea6fc2961e4ef194dcbfe56bb845534d0dc8098940c7e5c012a258bfec6701bd"
 
+[[package]]
+name = "x25519-dalek"
+version = "3.0.0-pre.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3d5d6ff67acd3945b933e592bfa7143db4fcbb2f871754b6b9fbd7847fc5aea"
+dependencies = [
+ "curve25519-dalek",
+ "rand_core",
+ "zeroize",
+]
+
 [[package]]
 name = "xcursor"
 version = "0.3.10"

useragent/rust/src/api/mod.rs

@@ -1,13 +1,15 @@
 use anyhow::anyhow;
+use arbiter_crypto::authn::{self, AuthChallenge, USERAGENT_CONTEXT};
 use flutter_rust_bridge::frb;
-use arbiter_crypto::authn::{self, USERAGENT_CONTEXT};
 
 #[frb(opaque)]
 pub struct MldsaKey(authn::SigningKey);
 
 impl MldsaKey {
     pub fn from_bytes(bytes: &[u8]) -> anyhow::Result<Self> {
-        let bytes: [u8; 32] = bytes.try_into().map_err(|_| anyhow!("Invalid key length"))?;
+        let bytes: [u8; 32] = bytes
+            .try_into()
+            .map_err(|_| anyhow!("Invalid key length"))?;
         Ok(Self(authn::SigningKey::from_seed(bytes)))
     }
 
@@ -27,3 +29,10 @@ impl MldsaKey {
         self.0.public_key().to_bytes().to_vec()
     }
 }
+
+pub fn format_challenge(random: Vec<u8>, timestamp: i64) -> Result<Vec<u8>, String> {
+    let challenge = AuthChallenge::from_parts(&random, timestamp)
+        .map_err(|_| "Invalid nonce length".to_string())?;
+
+    Ok(challenge.format())
+}

useragent/rust/src/frb_generated.rs

@@ -39,7 +39,7 @@ flutter_rust_bridge::frb_generated_boilerplate!(
     default_rust_auto_opaque = RustAutoOpaqueMoi,
 );
 pub(crate) const FLUTTER_RUST_BRIDGE_CODEGEN_VERSION: &str = "2.12.0";
-pub(crate) const FLUTTER_RUST_BRIDGE_CODEGEN_CONTENT_HASH: i32 = -437661335;
+pub(crate) const FLUTTER_RUST_BRIDGE_CODEGEN_CONTENT_HASH: i32 = 1247923898;
 
 // Section: executor
 
@@ -267,6 +267,40 @@ fn wire__crate__api__MldsaKey_to_bytes_impl(
         },
     )
 }
+fn wire__crate__api__format_challenge_impl(
+    port_: flutter_rust_bridge::for_generated::MessagePort,
+    ptr_: flutter_rust_bridge::for_generated::PlatformGeneralizedUint8ListPtr,
+    rust_vec_len_: i32,
+    data_len_: i32,
+) {
+    FLUTTER_RUST_BRIDGE_HANDLER.wrap_normal::<flutter_rust_bridge::for_generated::SseCodec, _, _>(
+        flutter_rust_bridge::for_generated::TaskInfo {
+            debug_name: "format_challenge",
+            port: Some(port_),
+            mode: flutter_rust_bridge::for_generated::FfiCallMode::Normal,
+        },
+        move || {
+            let message = unsafe {
+                flutter_rust_bridge::for_generated::Dart2RustMessageSse::from_wire(
+                    ptr_,
+                    rust_vec_len_,
+                    data_len_,
+                )
+            };
+            let mut deserializer =
+                flutter_rust_bridge::for_generated::SseDeserializer::new(message);
+            let api_random = <Vec<u8>>::sse_decode(&mut deserializer);
+            let api_timestamp = <i64>::sse_decode(&mut deserializer);
+            deserializer.end();
+            move |context| {
+                transform_result_sse::<_, String>((move || {
+                    let output_ok = crate::api::format_challenge(api_random, api_timestamp)?;
+                    Ok(output_ok)
+                })())
+            }
+        },
+    )
+}
 
 // Section: related_funcs
 
@@ -312,6 +346,13 @@ impl SseDecode for String {
     }
 }
 
+impl SseDecode for i64 {
+    // Codec=Sse (Serialization based), see doc to use other codecs
+    fn sse_decode(deserializer: &mut flutter_rust_bridge::for_generated::SseDeserializer) -> Self {
+        deserializer.cursor.read_i64::<NativeEndian>().unwrap()
+    }
+}
+
 impl SseDecode for Vec<u8> {
     // Codec=Sse (Serialization based), see doc to use other codecs
     fn sse_decode(deserializer: &mut flutter_rust_bridge::for_generated::SseDeserializer) -> Self {
@@ -371,6 +412,7 @@ fn pde_ffi_dispatcher_primary_impl(
         3 => wire__crate__api__MldsaKey_get_public_key_impl(port, ptr, rust_vec_len, data_len),
         4 => wire__crate__api__MldsaKey_sign_impl(port, ptr, rust_vec_len, data_len),
         5 => wire__crate__api__MldsaKey_to_bytes_impl(port, ptr, rust_vec_len, data_len),
+        6 => wire__crate__api__format_challenge_impl(port, ptr, rust_vec_len, data_len),
         _ => unreachable!(),
     }
 }
@@ -436,6 +478,13 @@ impl SseEncode for String {
     }
 }
 
+impl SseEncode for i64 {
+    // Codec=Sse (Serialization based), see doc to use other codecs
+    fn sse_encode(self, serializer: &mut flutter_rust_bridge::for_generated::SseSerializer) {
+        serializer.cursor.write_i64::<NativeEndian>(self).unwrap();
+    }
+}
+
 impl SseEncode for Vec<u8> {
     // Codec=Sse (Serialization based), see doc to use other codecs
     fn sse_encode(self, serializer: &mut flutter_rust_bridge::for_generated::SseSerializer) {