fix(useragent): unsafe, but working implementation of ml-dsa

useragent/rust/src/api/mod.rs

@@ -0,0 +1,29 @@
+use anyhow::anyhow;
+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"))?;
+        Ok(Self(authn::SigningKey::from_seed(bytes)))
+    }
+
+    pub fn to_bytes(&self) -> Vec<u8> {
+        self.0.to_seed().to_vec()
+    }
+
+    pub fn sign(&self, message: &[u8]) -> anyhow::Result<Vec<u8>> {
+        Ok(self.0.sign_message(message, USERAGENT_CONTEXT)?.to_bytes())
+    }
+
+    pub fn generate() -> Self {
+        Self(authn::SigningKey::generate())
+    }
+
+    pub fn get_public_key(&self) -> Vec<u8> {
+        self.0.public_key().to_bytes().to_vec()
+    }
+}