TrueCloudLab/rfc6979
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Reuse buffers for HMACs.

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This commit is contained in:
Coda Hale 2013-09-03 10:02:20 -07:00
parent 191cf5200e
commit 6a92cfbd65
1 changed files with 9 additions and 9 deletions
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18
rfc6979.go
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@ -26,10 +26,10 @@ import (
type HashFunc func() hash.Hash type HashFunc func() hash.Hash
// mac returns an HMAC of the given key and message. // mac returns an HMAC of the given key and message.
func (alg HashFunc) mac(k []byte, m []byte) []byte { func (alg HashFunc) mac(k, m, buf []byte) []byte {
h := hmac.New(alg, k) h := hmac.New(alg, k)
h.Write(m) h.Write(m)
return h.Sum(nil) return h.Sum(buf[:0])
} }
// https://tools.ietf.org/html/rfc6979#section-2.3.2 // https://tools.ietf.org/html/rfc6979#section-2.3.2
@ -89,16 +89,16 @@ func generateSecret(q, x *big.Int, alg HashFunc, hash []byte, test func(*big.Int
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...), k)
// Step E // Step E
v = alg.mac(k, v) v = alg.mac(k, v, v)
// Step F // Step F
k = alg.mac(k, append(append(v, 0x01), bx...)) k = alg.mac(k, append(append(v, 0x01), bx...), k)
// Step G // Step G
v = alg.mac(k, v) v = alg.mac(k, v, v)
// Step H // Step H
for { for {
@ -107,7 +107,7 @@ func generateSecret(q, x *big.Int, alg HashFunc, hash []byte, test func(*big.Int
// Step H2 // Step H2
for len(t) < qlen/8 { for len(t) < qlen/8 {
v = alg.mac(k, v) v = alg.mac(k, v, v)
t = append(t, v...) t = append(t, v...)
} }
@ -116,7 +116,7 @@ func generateSecret(q, x *big.Int, alg HashFunc, hash []byte, test func(*big.Int
if secret.Cmp(one) >= 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), k)
v = alg.mac(k, v) v = alg.mac(k, v, v)
} }
} }