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Move KDFNum to method param

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This commit is contained in:
Jonathan Rudenberg 2014-07-06 22:53:19 -07:00
parent 33aa69fc14
commit 0ab5aed0b2
2 changed files with 13 additions and 15 deletions
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18
box/box.go
View File

@ -45,7 +45,6 @@ type Crypter struct {
Key Key
PeerKey Key
ChainVar []byte
KDFNum uint8
scratch [64]byte
cc CipherContext
@ -66,7 +65,7 @@ func (c *Crypter) EncryptBody(dst, plaintext, authtext []byte, padLen int) []byt
return c.cc.Encrypt(dst, authtext, p)
}
func (c *Crypter) EncryptBox(dst []byte, ephKey *Key, plaintext []byte, padLen int) ([]byte, error) {
func (c *Crypter) EncryptBox(dst []byte, ephKey *Key, plaintext []byte, padLen int, kdfNum uint8) ([]byte, error) {
if len(c.ChainVar) == 0 {
c.ChainVar = make([]byte, CVLen)
}
@ -88,8 +87,8 @@ func (c *Crypter) EncryptBox(dst []byte, ephKey *Key, plaintext []byte, padLen i
dh1 := c.Cipher.DH(ephKey.Private, c.PeerKey.Public)
dh2 := c.Cipher.DH(c.Key.Private, c.PeerKey.Public)
cv1, cc1 := c.deriveKey(dh1, c.ChainVar)
cv2, cc2 := c.deriveKey(dh2, cv1)
cv1, cc1 := c.deriveKey(dh1, c.ChainVar, kdfNum)
cv2, cc2 := c.deriveKey(dh2, cv1, kdfNum+1)
c.ChainVar = cv2
dst = append(dst, ephKey.Public...)
@ -115,14 +114,14 @@ func (c *Crypter) cipher(cc []byte) CipherContext {
return c.cc
}
func (c *Crypter) DecryptBox(ciphertext []byte) ([]byte, error) {
func (c *Crypter) DecryptBox(ciphertext []byte, kdfNum uint8) ([]byte, error) {
if len(c.ChainVar) == 0 {
c.ChainVar = make([]byte, CVLen)
}
ephPubKey := ciphertext[:c.Cipher.DHLen()]
dh1 := c.Cipher.DH(c.Key.Private, ephPubKey)
cv1, cc1 := c.deriveKey(dh1, c.ChainVar)
cv1, cc1 := c.deriveKey(dh1, c.ChainVar, kdfNum)
header := ciphertext[:(2*c.Cipher.DHLen())+c.Cipher.MACLen()]
ciphertext = ciphertext[len(header):]
@ -137,7 +136,7 @@ func (c *Crypter) DecryptBox(ciphertext []byte) ([]byte, error) {
}
dh2 := c.Cipher.DH(c.Key.Private, senderPubKey)
cv2, cc2 := c.deriveKey(dh2, cv1)
cv2, cc2 := c.deriveKey(dh2, cv1, kdfNum+1)
c.ChainVar = cv2
body, err := c.cipher(cc2).Decrypt(header, ciphertext)
if err != nil {
@ -155,10 +154,9 @@ func (c *Crypter) DecryptBody(authtext, ciphertext []byte) ([]byte, error) {
return c.cc.Decrypt(authtext, ciphertext)
}
func (c *Crypter) deriveKey(dh, cv []byte) ([]byte, []byte) {
extra := append(c.Cipher.AppendName(c.scratch[:0]), c.KDFNum)
func (c *Crypter) deriveKey(dh, cv []byte, kdfNum uint8) ([]byte, []byte) {
extra := append(c.Cipher.AppendName(c.scratch[:0]), kdfNum)
k := DeriveKey(dh, cv, extra, CVLen+c.Cipher.CCLen())
c.KDFNum++
return k[:CVLen], k[CVLen:]
}

10
box/box_test.go
View File

@ -18,21 +18,21 @@ func (s *S) TestRoundtrip(c *C) {
plain := []byte("yellow submarines")
padLen := 2
ciphertext, err := enc.EncryptBox(nil, nil, plain, padLen)
ciphertext, err := enc.EncryptBox(nil, nil, plain, padLen, 0)
c.Assert(err, IsNil)
expectedLen := len(plain) + padLen + (2 * Noise255.DHLen()) + (2 * Noise255.MACLen()) + 4
c.Assert(ciphertext, HasLen, expectedLen, Commentf("expected: %d", expectedLen))
plaintext, err := dec.DecryptBox(ciphertext)
plaintext, err := dec.DecryptBox(ciphertext, 0)
c.Assert(err, IsNil)
c.Assert(plaintext, DeepEquals, plain)
plain[0] = 'Y'
ciphertext, err = enc.EncryptBox(nil, nil, plain, 0)
ciphertext, err = enc.EncryptBox(nil, nil, plain, 0, 1)
c.Assert(err, IsNil)
plaintext, err = dec.DecryptBox(ciphertext)
plaintext, err = dec.DecryptBox(ciphertext, 1)
c.Assert(err, IsNil)
c.Assert(plaintext, DeepEquals, plain)
}
@ -63,6 +63,6 @@ func BenchmarkEncryptBox(b *testing.B) {
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
enc.EncryptBox(nil, nil, []byte("yellow submarine"), 0)
enc.EncryptBox(nil, nil, []byte("yellow submarine"), 0, 0)
}
}