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Remove 9 allocs by using a buffer for key derivation

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This commit is contained in:
Jonathan Rudenberg 2014-07-03 22:29:21 -07:00
parent e8ef3d40dd
commit 908c2ac8a2
No known key found for this signature in database
GPG Key ID: E38D8C6BAA8C49AA
1 changed files with 34 additions and 29 deletions
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63
box/box.go
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@ -17,7 +17,7 @@ import (
)
type Ciphersuite interface {
Name() []byte
AppendName(dst []byte) []byte
DHLen() int
CCLen() int
MACLen() int
@ -32,28 +32,6 @@ type CipherContext interface {
Decrypt(authtext, ciphertext []byte) ([]byte, error)
}
func deriveKey(secret, extraData, info []byte, outputLen int) []byte {
output := make([]byte, 0, outputLen+sha512.Size)
t := make([]byte, 0, sha512.Size)
h := hmac.New(sha512.New, secret)
// info || (byte)c || t[0:32] || extra_data
data := make([]byte, len(info)+1+32+len(extraData))
copy(data, info)
copy(data[len(info)+1+32:], extraData)
var c byte
for len(output) < outputLen {
data[len(info)] = c
copy(data[len(info)+1:], t[:32])
h.Write(data)
t = h.Sum(t[:0])
h.Reset()
c++
output = append(output, t...)
}
return output[:outputLen]
}
const cvLen = 48
type Key struct {
@ -77,6 +55,8 @@ type Crypter struct {
ReceiverKey Key
ChainVar []byte
KDFNum int
keyBuf [512]byte
}
func (c *Crypter) Encrypt(dst []byte, ephKey *Key, plaintext []byte, padLen int) ([]byte, error) {
@ -146,20 +126,45 @@ func (c *Crypter) Decrypt(ciphertext []byte) ([]byte, error) {
}
func (c *Crypter) deriveKey(dh, cv []byte) []byte {
name := c.Cipher.Name()
k := deriveKey(dh, cv, strconv.AppendInt(name[:], int64(c.KDFNum), 10), cvLen+c.Cipher.CCLen())
// info || (byte)c || t[0:32] || extra_data
data := append(append(c.keyBuf[:0:256], cv...), 0)
data = data[:len(data)+32]
data = c.Cipher.AppendName(data)
data = strconv.AppendInt(data, int64(c.KDFNum), 10)
output := c.keyBuf[256 : len(c.keyBuf)-sha512.Size : len(c.keyBuf)-sha512.Size]
t := c.keyBuf[len(c.keyBuf)-sha512.Size:]
k := deriveKey(dh, data, output, t, cvLen, cvLen+c.Cipher.CCLen())
c.KDFNum++
return k
}
func deriveKey(secret, data, output, t []byte, infoLen, outputLen int) []byte {
h := hmac.New(sha512.New, secret)
var c byte
for len(output) < outputLen {
data[infoLen] = c
copy(data[infoLen+1:], t[:32])
h.Write(data)
t = h.Sum(t[:0])
h.Reset()
c++
output = append(output, t...)
}
return output[:outputLen]
}
var Noise255 = noise255{}
type noise255 struct{}
func (noise255) Name() []byte { return []byte("Noise255") }
func (noise255) DHLen() int { return 32 }
func (noise255) CCLen() int { return 40 }
func (noise255) MACLen() int { return 16 }
func (noise255) AppendName(dst []byte) []byte {
return append(dst, "Noise255\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"...)
}
func (noise255) DHLen() int { return 32 }
func (noise255) CCLen() int { return 40 }
func (noise255) MACLen() int { return 16 }
func (noise255) GenerateKey(random io.Reader) (Key, error) {
var pubKey, privKey [32]byte