TrueCloudLab/rfc6979
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Small, tender improvements.

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This commit is contained in:
Coda Hale 2013-08-26 19:48:12 -07:00
parent b8b070246b
commit 26d3e208da
2 changed files with 6 additions and 2 deletions
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1
ecdsa.go
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@ -6,6 +6,7 @@ import (
"math/big" "math/big"
) )
// copied from crypto/ecdsa
func hashToInt(hash []byte, c elliptic.Curve) *big.Int { func hashToInt(hash []byte, c elliptic.Curve) *big.Int {
orderBits := c.Params().N.BitLen() orderBits := c.Params().N.BitLen()
orderBytes := (orderBits + 7) / 8 orderBytes := (orderBits + 7) / 8

7
rfc6979.go
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@ -27,12 +27,14 @@ import (
// A function which provides a fresh Hash (e.g., sha256.New). // A function which provides a fresh Hash (e.g., sha256.New).
type HashAlgorithm func() hash.Hash type HashAlgorithm func() hash.Hash
// digest returns a digest of the given message.
func (alg HashAlgorithm) digest(m []byte) []byte { func (alg HashAlgorithm) digest(m []byte) []byte {
h := alg() h := alg()
h.Write(m) h.Write(m)
return h.Sum(nil) return h.Sum(nil)
} }
// mac returns an HMAC of the given key and message.
func (alg HashAlgorithm) mac(k []byte, m []byte) []byte { func (alg HashAlgorithm) mac(k []byte, m []byte) []byte {
h := hmac.New(alg, k) h := hmac.New(alg, k)
h.Write(m) h.Write(m)
@ -80,6 +82,8 @@ func bits2octets(in []byte, q *big.Int, qlen, rolen int) []byte {
return int2octets(z2, rolen) return int2octets(z2, rolen)
} }
var one = big.NewInt(1)
// https://tools.ietf.org/html/rfc6979#section-3.2 // https://tools.ietf.org/html/rfc6979#section-3.2
func generateSecret(q, x *big.Int, alg HashAlgorithm, hash []byte, test func(*big.Int) bool) { func generateSecret(q, x *big.Int, alg HashAlgorithm, hash []byte, test func(*big.Int) bool) {
qlen := q.BitLen() qlen := q.BitLen()
@ -94,7 +98,6 @@ func generateSecret(q, x *big.Int, alg HashAlgorithm, hash []byte, test func(*bi
k := bytes.Repeat([]byte{0x00}, holen) k := bytes.Repeat([]byte{0x00}, holen)
// Step D // Step D
k = alg.mac(k, append(append(v, 0x00), bx...)) k = alg.mac(k, append(append(v, 0x00), bx...))
// Step E // Step E
@ -119,7 +122,7 @@ func generateSecret(q, x *big.Int, alg HashAlgorithm, hash []byte, test func(*bi
// Step H3 // Step H3
secret := bits2int(t, qlen) secret := bits2int(t, qlen)
if secret.Cmp(big.NewInt(1)) >= 0 && secret.Cmp(q) < 0 && test(secret) { if secret.Cmp(one) >= 0 && secret.Cmp(q) < 0 && test(secret) {
return return
} }
k = alg.mac(k, append(v, 0x00)) k = alg.mac(k, append(v, 0x00))