Add Transaction::sign.

While I don't love the introduction of empty_signed, it's practically fine.

Cargo.lock

@@ -10769,7 +10769,6 @@ dependencies = [
  "parity-scale-codec",
  "rand 0.8.5",
  "rand_chacha 0.3.1",
- "rand_core 0.6.4",
  "schnorr-signatures",
  "serai-db",
  "subtle",

coordinator/Cargo.toml

@@ -17,6 +17,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 async-trait = "0.1"
 
 zeroize = "^1.5"
+rand_core = "0.6"
 
 blake2 = "0.10"
 
@@ -40,6 +41,4 @@ log = "0.4"
 tokio = { version = "1", features = ["full"] }
 
 [dev-dependencies]
-rand_core = "0.6"
-
 tributary = { package = "tributary-chain", path = "./tributary", features = ["tests"] }

coordinator/src/tests/tributary/dkg.rs

@@ -1,11 +1,9 @@
 use core::time::Duration;
 
 use zeroize::Zeroizing;
-
 use rand_core::{RngCore, OsRng};
 
-use ciphersuite::{group::ff::Field, Ciphersuite, Ristretto};
-use schnorr::SchnorrSignature;
+use ciphersuite::{Ciphersuite, Ristretto};
 use frost::Participant;
 
 use tokio::time::sleep;
@@ -17,7 +15,7 @@ use processor_messages::{
   CoordinatorMessage,
 };
 
-use tributary::{Signed, Transaction as TransactionTrait, Tributary};
+use tributary::Tributary;
 
 use crate::{
   processor::MemProcessor,
@@ -39,41 +37,14 @@ async fn dkg_commitments_test() {
   let mut txs = vec![];
   // Create DKG commitments for each key
   for key in &keys {
-    let pub_key = Ristretto::generator() * **key;
-
     let attempt = 0;
     let mut commitments = vec![0; 256];
     OsRng.fill_bytes(&mut commitments);
 
-    // Create the TX with a null signature so we can get its sig hash
-    let tx = Transaction::DkgCommitments(
-      attempt,
-      commitments.clone(),
-      Signed {
-        signer: pub_key,
-        nonce: 0,
-        signature: SchnorrSignature::<Ristretto> {
-          R: Ristretto::generator(),
-          s: <Ristretto as Ciphersuite>::F::ZERO,
-        },
-      },
-    );
-
-    // Re-create it with the actual signature
-    // We could mutate the existing one, we'd just have to match to the DkgCommitments enum variant
-    txs.push(Transaction::DkgCommitments(
-      attempt,
-      commitments,
-      Signed {
-        signer: pub_key,
-        nonce: 0,
-        signature: SchnorrSignature::<Ristretto>::sign(
-          key,
-          Zeroizing::new(<Ristretto as Ciphersuite>::F::random(&mut OsRng)),
-          tx.sig_hash(spec.genesis()),
-        ),
-      },
-    ));
+    let mut tx =
+      Transaction::DkgCommitments(attempt, commitments.clone(), Transaction::empty_signed());
+    tx.sign(&mut OsRng, spec.genesis(), key, 0);
+    txs.push(tx);
   }
 
   let mut last_block = tributaries[0].1.tip();

coordinator/src/tests/tributary/tx.rs

@@ -1,17 +1,12 @@
 use core::time::Duration;
 
-use zeroize::Zeroizing;
-
 use rand_core::{RngCore, OsRng};
 
-use ciphersuite::{group::ff::Field, Ciphersuite, Ristretto};
-use schnorr::SchnorrSignature;
-
 use tokio::time::sleep;
 
 use serai_db::MemDb;
 
-use tributary::{Signed, Transaction as TransactionTrait, Tributary};
+use tributary::Tributary;
 
 use crate::{
   LocalP2p,
@@ -33,41 +28,15 @@ async fn tx_test() {
   let sender =
     usize::try_from(OsRng.next_u64() % u64::try_from(tributaries.len()).unwrap()).unwrap();
   let key = keys[sender].clone();
-  let pub_key = Ristretto::generator() * *key;
 
   let attempt = 0;
   let mut commitments = vec![0; 256];
   OsRng.fill_bytes(&mut commitments);
 
   // Create the TX with a null signature so we can get its sig hash
-  let tx = Transaction::DkgCommitments(
-    attempt,
-    commitments.clone(),
-    Signed {
-      signer: pub_key,
-      nonce: 0,
-      signature: SchnorrSignature::<Ristretto> {
-        R: Ristretto::generator(),
-        s: <Ristretto as Ciphersuite>::F::ZERO,
-      },
-    },
-  );
-
-  // Re-create it with the actual signature
-  // We could mutate the existing one, we'd just have to match to the DkgCommitments enum variant
-  let tx = Transaction::DkgCommitments(
-    attempt,
-    commitments,
-    Signed {
-      signer: pub_key,
-      nonce: 0,
-      signature: SchnorrSignature::<Ristretto>::sign(
-        &key,
-        Zeroizing::new(<Ristretto as Ciphersuite>::F::random(&mut OsRng)),
-        tx.sig_hash(spec.genesis()),
-      ),
-    },
-  );
+  let mut tx =
+    Transaction::DkgCommitments(attempt, commitments.clone(), Transaction::empty_signed());
+  tx.sign(&mut OsRng, spec.genesis(), &key, 0);
 
   assert!(tributaries[sender].1.add_transaction(tx.clone()).await);
   // Sleep for two blocks

coordinator/src/tributary/mod.rs

@@ -1,9 +1,14 @@
+use core::ops::Deref;
 use std::{io, collections::HashMap};
 
+use zeroize::Zeroizing;
+use rand_core::{RngCore, CryptoRng};
+
 use blake2::{Digest, Blake2s256};
 use transcript::{Transcript, RecommendedTranscript};
 
-use ciphersuite::{Ciphersuite, Ristretto};
+use ciphersuite::{group::ff::Field, Ciphersuite, Ristretto};
+use schnorr::SchnorrSignature;
 use frost::Participant;
 
 use scale::Encode;
@@ -349,3 +354,53 @@ impl TransactionTrait for Transaction {
     Ok(())
   }
 }
+
+impl Transaction {
+  // Used to initially construct transactions so we can then get sig hashes and perform signing
+  pub fn empty_signed() -> Signed {
+    Signed {
+      signer: Ristretto::generator(),
+      nonce: 0,
+      signature: SchnorrSignature::<Ristretto> {
+        R: Ristretto::generator(),
+        s: <Ristretto as Ciphersuite>::F::ZERO,
+      },
+    }
+  }
+
+  // Sign a transaction
+  pub fn sign<R: RngCore + CryptoRng>(
+    &mut self,
+    rng: &mut R,
+    genesis: [u8; 32],
+    key: &Zeroizing<<Ristretto as Ciphersuite>::F>,
+    nonce: u32,
+  ) {
+    fn signed(tx: &mut Transaction) -> &mut Signed {
+      match tx {
+        Transaction::DkgCommitments(_, _, ref mut signed) => signed,
+        Transaction::DkgShares(_, _, ref mut signed) => signed,
+
+        Transaction::ExternalBlock(_) => panic!("signing ExternalBlock"),
+        Transaction::SubstrateBlock(_) => panic!("signing SubstrateBlock"),
+
+        Transaction::BatchPreprocess(ref mut data) => &mut data.signed,
+        Transaction::BatchShare(ref mut data) => &mut data.signed,
+
+        Transaction::SignPreprocess(ref mut data) => &mut data.signed,
+        Transaction::SignShare(ref mut data) => &mut data.signed,
+      }
+    }
+
+    let signed_ref = signed(self);
+    signed_ref.signer = Ristretto::generator() * key.deref();
+    signed_ref.nonce = nonce;
+
+    let sig_hash = self.sig_hash(genesis);
+    signed(self).signature = SchnorrSignature::<Ristretto>::sign(
+      key,
+      Zeroizing::new(<Ristretto as Ciphersuite>::F::random(rng)),
+      sig_hash,
+    );
+  }
+}

coordinator/tributary/Cargo.toml

@@ -36,7 +36,6 @@ tokio = { version = "1", features = ["macros", "sync", "time", "rt"] }
 
 [dev-dependencies]
 zeroize = "^1.5"
-rand_core = "0.6"
 
 [features]
 tests = []