secp256k1: Direct byte clears.

dcrec/secp256k1/ecdsa/signature.go

@@ -22,10 +22,6 @@ import (
 //     https://www.secg.org/sec1-v2.pdf
 
 var (
-	// zero32 is an array of 32 bytes used for the purposes of zeroing and is
-	// defined here to avoid extra allocations.
-	zero32 = [32]byte{}
-
 	// orderAsFieldVal is the order of the secp256k1 curve group stored as a
 	// field value.  It is provided here to avoid the need to create it multiple
 	// times.
@@ -140,7 +136,7 @@ func (sig *Signature) Serialize() []byte {
 
 // zeroArray32 zeroes the provided 32-byte buffer.
 func zeroArray32(b *[32]byte) {
-	copy(b[:], zero32[:])
+	*b = [32]byte{}
 }
 
 // fieldToModNScalar converts a field value to scalar modulo the group order and

dcrec/secp256k1/field.go

@@ -198,16 +198,7 @@ func (f FieldVal) String() string {
 //	Output Normalized: Yes
 //	Output Max Magnitude: 1
 func (f *FieldVal) Zero() {
-	f.n[0] = 0
-	f.n[1] = 0
-	f.n[2] = 0
-	f.n[3] = 0
-	f.n[4] = 0
-	f.n[5] = 0
-	f.n[6] = 0
-	f.n[7] = 0
-	f.n[8] = 0
-	f.n[9] = 0
+	f.n = [10]uint32{}
 }
 
 // Set sets the field value equal to the passed value in constant time.  The

dcrec/secp256k1/modnscalar.go

@@ -95,12 +95,6 @@ const (
 	uint32Mask = 0xffffffff
 )
 
-var (
-	// zero32 is an array of 32 bytes used for the purposes of zeroing and is
-	// defined here to avoid extra allocations.
-	zero32 = [32]byte{}
-)
-
 // ModNScalar implements optimized 256-bit constant-time fixed-precision
 // arithmetic over the secp256k1 group order. This means all arithmetic is
 // performed modulo:
@@ -169,14 +163,7 @@ func (s *ModNScalar) Set(val *ModNScalar) *ModNScalar {
 // already set to zero.  This function can be useful to clear an existing scalar
 // for reuse.
 func (s *ModNScalar) Zero() {
-	s.n[0] = 0
-	s.n[1] = 0
-	s.n[2] = 0
-	s.n[3] = 0
-	s.n[4] = 0
-	s.n[5] = 0
-	s.n[6] = 0
-	s.n[7] = 0
+	s.n = [8]uint32{}
 }
 
 // IsZeroBit returns 1 when the scalar is equal to zero or 0 otherwise in
@@ -309,7 +296,7 @@ func (s *ModNScalar) SetBytes(b *[32]byte) uint32 {
 
 // zeroArray32 zeroes the provided 32-byte buffer.
 func zeroArray32(b *[32]byte) {
-	copy(b[:], zero32[:])
+	*b = [32]byte{}
 }
 
 // SetByteSlice interprets the provided slice as a 256-bit big-endian unsigned

dcrec/secp256k1/schnorr/signature.go

@@ -237,9 +237,7 @@ func (sig *Signature) Verify(hash []byte, pubKey *secp256k1.PublicKey) bool {
 
 // zeroArray zeroes the memory of a scalar array.
 func zeroArray(a *[scalarSize]byte) {
-	for i := 0; i < scalarSize; i++ {
-		a[i] = 0x00
-	}
+	*a = [scalarSize]byte{}
 }
 
 // schnorrSign generates an EC-Schnorr-DCRv0 signature over the secp256k1 curve