spaces: a member wears a key minted for that room alone, so a roster stops naming personas

crates/persona-state/src/lib.rs

@@ -12,7 +12,7 @@
 //! `profile_sign_payload` / `asset_sign_payload` return exactly what the
 //! identity delegate must be handed for each.
 
-use ed25519_dalek::{Signature, Verifier, VerifyingKey};
+use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
 use serde::{Deserialize, Serialize};
 
 pub mod slsk_link;
@@ -93,6 +93,19 @@ pub(crate) fn signable(domain: &str, payload: &[u8]) -> Vec<u8> {
     msg
 }
 
+/// Sign with a raw ed25519 secret in an explicit domain. The delegate holds
+/// the persona and signs for it; these are the room-local keys it does not
+/// hold, so their signing lives beside the verification it has to match.
+/// Deterministic — no entropy, which is what keeps getrandom out of wasm.
+pub fn sign_local(domain: &str, secret: &[u8; 32], payload: &[u8]) -> Vec<u8> {
+    SigningKey::from_bytes(secret).sign(&signable(domain, payload)).to_bytes().to_vec()
+}
+
+/// The public half of a raw ed25519 secret.
+pub fn public_of(secret: &[u8; 32]) -> [u8; 32] {
+    SigningKey::from_bytes(secret).verifying_key().to_bytes()
+}
+
 pub fn verify_sig(public: &[u8; 32], payload: &[u8], sig: &[u8]) -> bool {
     verify_sig_in(SIGN_DOMAIN, public, payload, sig)
 }