mixing: Optimize mix message signature funcs.

mixing/signatures.go

@@ -1,18 +1,17 @@
-// Copyright (c) 2023-2024 The Decred developers
+// Copyright (c) 2023-2026 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
 package mixing
 
 import (
-	"bytes"
-	"fmt"
+	"encoding/hex"
 	"hash"
+	"strconv"
 
 	"github.com/decred/dcrd/crypto/blake256"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4/schnorr"
-	"github.com/decred/dcrd/wire"
 )
 
 const tag = "decred-mix-signature"
@@ -46,8 +45,6 @@ func VerifySignedMessage(m Signed) bool {
 	m.WriteSignedData(h)
 	sigHash := h.Sum256()
 
-	h.Reset()
-
 	command := m.Command()
 	sid := m.Sid()
 	run := m.GetRun()
@@ -56,6 +53,7 @@ func VerifySignedMessage(m Signed) bool {
 		run = 0
 	}
 
+	h.Reset()
 	return verify(h, m.Pub(), m.Sig(), sigHash[:], command, sid, run)
 }
 
@@ -76,26 +74,15 @@ func sign(priv *secp256k1.PrivateKey, m Signed) ([]byte, error) {
 	m.WriteSignedData(h)
 	sigHash := h.Sum256()
 
-	h.Reset()
-
 	sid := m.Sid()
 	run := m.GetRun()
 	if len(sid) != 32 {
 		sid = zeroSID[:]
 		run = 0
 	}
 
-	buf := new(bytes.Buffer)
-	buf.Grow(len(tag) + wire.CommandSize +
-		64 + // sid
-		4 + // run
-		64 + // sigHash
-		4, // commas
-	)
-	fmt.Fprintf(buf, tag+",%s,%x,%d,%x", m.Command(), sid, run, sigHash[:])
-	h.Write(buf.Bytes())
-
-	hash := h.Sum256()
+	h.Reset()
+	hash := schnorrHash(h, m.Command(), sid, run, sigHash[:])
 	sig, err := schnorr.Sign(priv, hash[:])
 	if err != nil {
 		return nil, err
@@ -116,17 +103,21 @@ func verify(h *blake256.Hasher256, pk []byte, sig []byte, sigHash []byte, comman
 		return false
 	}
 
-	h.Reset()
-
-	buf := new(bytes.Buffer)
-	buf.Grow(len(tag) + wire.CommandSize +
-		64 + // sid
-		4 + // run
-		64 + // sigHash
-		4, // commas
-	)
-	fmt.Fprintf(buf, tag+",%s,%x,%d,%x", command, sid, run, sigHash)
-	h.Write(buf.Bytes())
-	hash := h.Sum256()
+	hash := schnorrHash(h, command, sid, run, sigHash)
 	return sigParsed.Verify(hash[:], pkParsed)
 }
+
+func schnorrHash(h *blake256.Hasher256, command string, sid []byte, run uint32, sigHash []byte) [32]byte {
+	buf := make([]byte, 64)
+
+	h.WriteBytes([]byte(tag))
+	h.WriteByte(',')
+	h.WriteString(command)
+	h.WriteByte(',')
+	h.WriteBytes(hex.AppendEncode(buf[:0], sid))
+	h.WriteByte(',')
+	h.WriteBytes(strconv.AppendUint(buf[:0], uint64(run), 10))
+	h.WriteByte(',')
+	h.WriteBytes(hex.AppendEncode(buf[:0], sigHash))
+	return h.Sum256()
+}

mixing/signatures_test.go

@@ -0,0 +1,104 @@
+// Copyright (c) 2026 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package mixing
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+
+	"github.com/decred/dcrd/dcrec/secp256k1/v4"
+	"github.com/decred/dcrd/wire"
+)
+
+var (
+	testPrivKey = secp256k1.PrivKeyFromBytes([]byte{31: 1})
+	testPubKey  = testPrivKey.PubKey()
+)
+
+func hexDecode(tb testing.TB, s string) []byte {
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		tb.Fatalf("Hex decode failed: %v", err)
+	}
+	return b
+}
+
+func fakePR(tb testing.TB) *wire.MsgMixPairReq {
+	var id [33]byte
+	copy(id[:], testPubKey.SerializeCompressed())
+	utxos := []wire.MixPairReqUTXO{{
+		OutPoint: wire.OutPoint{
+			Hash:  [32]byte{31: 1},
+			Index: 2,
+			Tree:  3,
+		},
+		Script:    []byte{4, 5, 6},
+		PubKey:    []byte{31: 7},
+		Signature: []byte{31: 8},
+		Opcode:    9,
+	}}
+	change := &wire.TxOut{
+		Value:    10,
+		Version:  11,
+		PkScript: []byte{12, 13, 14},
+	}
+	pr, err := wire.NewMsgMixPairReq(id, 15, 16, "script class", 17, 18, 19, 20, utxos, change, 21, 22)
+	if err != nil {
+		tb.Fatal(err)
+	}
+	return pr
+}
+
+const wantSig = "1ffdddfb26b2955b3cf46c9e98671d11d1fd91619da4e85edb840786f661b6ab6824c83923f596a990613fce97d995d9d50a89ecb23841c9c10a80a47f18b50a"
+
+func TestSignMessage(t *testing.T) {
+	pr := fakePR(t)
+
+	if err := SignMessage(pr, testPrivKey); err != nil {
+		t.Fatalf("Failed to sign message: %v", err)
+	}
+
+	if !bytes.Equal(pr.Signature[:], hexDecode(t, wantSig)) {
+		t.Fatalf("Signature does not match expected (got: %x want: %s)", pr.Signature[:], wantSig)
+	}
+}
+
+func TestVerifySignedMessage(t *testing.T) {
+	pr := fakePR(t)
+
+	if err := SignMessage(pr, testPrivKey); err != nil {
+		t.Fatalf("Failed to sign message: %v", err)
+	}
+
+	if !VerifySignedMessage(pr) {
+		t.Fatalf("VerifySignedMessage invalid signature %x", pr.Signature[:])
+	}
+}
+
+func BenchmarkSignMessage(b *testing.B) {
+	pr := fakePR(b)
+
+	for b.Loop() {
+		err := SignMessage(pr, testPrivKey)
+		if err != nil {
+			b.Fatalf("Failed to sign message: %v", err)
+		}
+	}
+}
+
+func BenchmarkVerifySignedMessage(b *testing.B) {
+	pr := fakePR(b)
+	err := SignMessage(pr, testPrivKey)
+	if err != nil {
+		b.Fatalf("Failed to sign message: %v", err)
+	}
+
+	for b.Loop() {
+		if !VerifySignedMessage(pr) {
+			b.Fatalf("VerifySignedMessage invalid signature %x", pr.Signature[:])
+		}
+	}
+}