mixing: Avoid hash.Hash and Sum(nil) calls

mixing/dcnet.go

@@ -15,9 +15,8 @@ import (
 // SRMixPads creates a vector of exponential DC-net pads from a vector of
 // shared secrets with each participating peer in the DC-net.
 func SRMixPads(kp [][]byte, my uint32) []*big.Int {
-	h := blake256.New()
+	h := blake256.NewHasher256()
 	scratch := make([]byte, 8)
-	digest := make([]byte, blake256.Size)
 	pads := make([]*big.Int, len(kp))
 	partialPad := new(big.Int)
 	for j := uint32(0); j < uint32(len(kp)); j++ {
@@ -30,8 +29,8 @@ func SRMixPads(kp [][]byte, my uint32) []*big.Int {
 			h.Reset()
 			h.Write(kp[i])
 			h.Write(scratch)
-			digest = h.Sum(digest[:0])
-			partialPad.SetBytes(digest)
+			digest := h.Sum256()
+			partialPad.SetBytes(digest[:])
 			if my > i {
 				pads[j].Add(pads[j], partialPad)
 			} else {

mixing/mixclient/client.go

@@ -417,7 +417,7 @@ func NewClient(w Wallet) *Client {
 		height:          height,
 		warming:         make(chan struct{}),
 		workQueue:       make(chan *queueWork, runtime.NumCPU()),
-		blake256Hasher:  blake256.New(),
+		blake256Hasher:  blake256.NewHasher256(),
 		epoch:           w.Mixpool().Epoch(),
 		stopping:        make(chan struct{}),
 	}

mixing/sid.go

@@ -17,7 +17,7 @@ import (
 // deriveSessionID creates the mix session identifier from an initial sorted
 // slice of PR message hashes.
 func deriveSessionID(seenPRs []chainhash.Hash, epoch uint64) [32]byte {
-	h := blake256.New()
+	h := blake256.NewHasher256()
 	buf := make([]byte, 8)
 
 	h.Write([]byte("decred-mix-session"))
@@ -29,7 +29,7 @@ func deriveSessionID(seenPRs []chainhash.Hash, epoch uint64) [32]byte {
 		h.Write(seenPRs[i][:])
 	}
 
-	return *(*[32]byte)(h.Sum(nil))
+	return h.Sum256()
 }
 
 // SortPRsForSession performs an in-place sort of prs, moving each pair

mixing/signatures.go

@@ -42,9 +42,9 @@ func SignMessage(m Signed, priv *secp256k1.PrivateKey) error {
 // VerifySignedMessage verifies that a signed message carries a valid
 // signature for the represented identity.
 func VerifySignedMessage(m Signed) bool {
-	h := blake256.New()
+	h := blake256.NewHasher256()
 	m.WriteSignedData(h)
-	sigHash := h.Sum(nil)
+	sigHash := h.Sum256()
 
 	h.Reset()
 
@@ -56,7 +56,7 @@ func VerifySignedMessage(m Signed) bool {
 		run = 0
 	}
 
-	return verify(h, m.Pub(), m.Sig(), sigHash, command, sid, run)
+	return verify(h, m.Pub(), m.Sig(), sigHash[:], command, sid, run)
 }
 
 // VerifySignature verifies a message signature from its signature hash and
@@ -65,16 +65,16 @@ func VerifySignedMessage(m Signed) bool {
 // the same public key, and demonstrating this can be used to prove malicious
 // behavior by sending different versions of messages through the network.
 func VerifySignature(pub, sig, sigHash []byte, command string, sid []byte, run uint32) bool {
-	h := blake256.New()
+	h := blake256.NewHasher256()
 	return verify(h, pub, sig, sigHash, command, sid, run)
 }
 
 var zeroSID [32]byte
 
 func sign(priv *secp256k1.PrivateKey, m Signed) ([]byte, error) {
-	h := blake256.New()
+	h := blake256.NewHasher256()
 	m.WriteSignedData(h)
-	sigHash := h.Sum(nil)
+	sigHash := h.Sum256()
 
 	h.Reset()
 
@@ -92,17 +92,18 @@ func sign(priv *secp256k1.PrivateKey, m Signed) ([]byte, error) {
 		64 + // sigHash
 		4, // commas
 	)
-	fmt.Fprintf(buf, tag+",%s,%x,%d,%x", m.Command(), sid, run, sigHash)
+	fmt.Fprintf(buf, tag+",%s,%x,%d,%x", m.Command(), sid, run, sigHash[:])
 	h.Write(buf.Bytes())
 
-	sig, err := schnorr.Sign(priv, h.Sum(nil))
+	hash := h.Sum256()
+	sig, err := schnorr.Sign(priv, hash[:])
 	if err != nil {
 		return nil, err
 	}
 	return sig.Serialize(), nil
 }
 
-func verify(h hash.Hash, pk []byte, sig []byte, sigHash []byte, command string, sid []byte, run uint32) bool {
+func verify(h *blake256.Hasher256, pk []byte, sig []byte, sigHash []byte, command string, sid []byte, run uint32) bool {
 	if len(pk) != secp256k1.PubKeyBytesLenCompressed {
 		return false
 	}
@@ -126,5 +127,6 @@ func verify(h hash.Hash, pk []byte, sig []byte, sigHash []byte, command string,
 	)
 	fmt.Fprintf(buf, tag+",%s,%x,%d,%x", command, sid, run, sigHash)
 	h.Write(buf.Bytes())
-	return sigParsed.Verify(h.Sum(nil), pkParsed)
+	hash := h.Sum256()
+	return sigParsed.Verify(hash[:], pkParsed)
 }

mixing/utxoproof/utxoproof.go

@@ -5,8 +5,6 @@
 package utxoproof
 
 import (
-	"encoding/binary"
-
 	"github.com/decred/dcrd/crypto/blake256"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4/schnorr"
@@ -23,7 +21,7 @@ const (
 	secp256k1P2PKH = "P2PKH(EC-Schnorr-DCRv0)"
 )
 
-var sep = []byte{','}
+const sep = ","
 
 // The signature hash is created from the serialization of:
 //   tag , scheme , expiry pubkey
@@ -43,17 +41,14 @@ type Secp256k1KeyPair struct {
 func (k *Secp256k1KeyPair) SignUtxoProof(expires uint32) ([]byte, error) {
 	const scheme = secp256k1P2PKH
 
-	h := blake256.New()
-	h.Write([]byte(tag))
-	h.Write(sep)
-	h.Write([]byte(scheme))
-	h.Write(sep)
-	expiresBytes := binary.BigEndian.AppendUint32(make([]byte, 0, 4), expires)
-	h.Write(expiresBytes)
-	h.Write(k.Pub)
-	hash := h.Sum(nil)
+	h := blake256.NewHasher256()
+	const preamble = tag + sep + scheme + sep
+	h.WriteBytes([]byte(preamble))
+	h.WriteUint32BE(expires)
+	h.WriteBytes(k.Pub)
+	hash := h.Sum256()
 
-	sig, err := schnorr.Sign(k.Priv, hash)
+	sig, err := schnorr.Sign(k.Priv, hash[:])
 	if err != nil {
 		return nil, err
 	}
@@ -76,15 +71,12 @@ func ValidateSecp256k1P2PKH(pubkey, proof []byte, expires uint32) bool {
 		return false
 	}
 
-	h := blake256.New()
-	h.Write([]byte(tag))
-	h.Write(sep)
-	h.Write([]byte(scheme))
-	h.Write(sep)
-	expiresBytes := binary.BigEndian.AppendUint32(make([]byte, 0, 4), expires)
-	h.Write(expiresBytes)
+	h := blake256.NewHasher256()
+	const preamble = tag + sep + scheme + sep
+	h.WriteBytes([]byte(preamble))
+	h.WriteUint32BE(expires)
 	h.Write(pubkey)
-	hash := h.Sum(nil)
+	hash := h.Sum256()
 
-	return proofParsed.Verify(hash, pubkeyParsed)
+	return proofParsed.Verify(hash[:], pubkeyParsed)
 }