Avoid recomputation of the credential public key during verification

ooniauth-core/benches/bench_server.rs

@@ -15,7 +15,7 @@ fn setup() -> (ThreadRng, UserState, ServerState) {
 // For now we will only care about server functions, specially handling submit and
 // registration, since those are the most important bottleneck for our backend
 fn bench_registration(c: &mut Criterion) {
-    let (mut rng, user, mut server) = setup();
+    let (mut rng, user, server) = setup();
 
     // Create the request
     let (registration_req, _) = user.request(&mut rng).unwrap();
@@ -25,14 +25,14 @@ fn bench_registration(c: &mut Criterion) {
 }
 
 fn bench_submit(c: &mut Criterion) {
-    let (mut rng, mut user, mut server) = setup();
+    let (mut rng, mut user, server) = setup();
 
     c.bench_function("server.handle_submit", |b| {
         let (registration_req, reg_state) = user.request(&mut rng).unwrap();
         let resp = server.open_registration(registration_req).unwrap();
         user.handle_response(reg_state, resp)
             .expect("Should handle response properly");
-        let today = server.today();
+        let today = ServerState::today();
         let cc = "VE";
         let asn = "AS1234";
 
@@ -52,8 +52,8 @@ fn bench_submit(c: &mut Criterion) {
                 black_box(&mut rng),
                 black_box(req.clone()),
                 black_box(&nym),
-                black_box(cc.into()),
-                black_box(asn.into()),
+                black_box(cc),
+                black_box(asn),
                 black_box(age_range.clone()),
                 black_box(msm_range.clone()),
             )

ooniauth-core/src/registration.rs

@@ -21,6 +21,19 @@ CMZ! { UserAuthCredential:
     measurement_count
 }
 
+impl UserAuthCredential {
+    /// Set the public key and private key for this credential. Assumes the keypair is well-formed.
+    pub(crate) fn set_keypair(
+        &mut self,
+        privkey: CMZPrivkey<G>,
+        pubkey: CMZPubkey<G>,
+    ) -> &mut Self {
+        self.privkey = privkey;
+        self.pubkey = pubkey;
+        self
+    }
+}
+
 muCMZProtocol! {open_registration,
     ,
     UAC: UserAuthCredential { nym_id: J, age: S, measurement_count: I},
@@ -76,7 +89,7 @@ impl ServerState {
             SESSION_ID,
             recvreq,
             |UAC: &mut UserAuthCredential| {
-                UAC.set_privkey(&self.sk);
+                UAC.set_keypair(self.sk.clone(), self.pp.clone());
                 UAC.measurement_count = Some(Scalar::ZERO);
                 UAC.age = Some(ServerState::today().into());
                 Ok(())

ooniauth-core/src/submit.rs

@@ -170,14 +170,15 @@ impl ServerState {
         };
 
         let server_sk = self.sk.clone();
+        let server_pp = self.pp.clone();
         match submit::handle(
             rng,
             SESSION_ID,
             recvreq,
             move |Old: &mut UserAuthCredential, New: &mut UserAuthCredential| {
                 // Set the private key for the credentials - this is essential for the protocol
-                Old.set_privkey(&server_sk);
-                New.set_privkey(&server_sk);
+                Old.set_keypair(server_sk.clone(), server_pp.clone());
+                New.set_keypair(server_sk.clone(), server_pp.clone());
 
                 // The protocol should populate Old and New from the client's proof
                 // We don't set the values here - they come from the client's proof
@@ -231,7 +232,7 @@ mod tests {
         let rng = &mut rand::thread_rng();
 
         // Setup server and user
-        let mut server_state = ServerState::new(rng);
+        let server_state = ServerState::new(rng);
         let mut user_state = UserState::new(server_state.public_parameters());
 
         // First do registration to get a credential