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lioness.go
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lioness.go
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// lioness.go - A LIONESS-BLAKE2b-ChaCha20 implementation.
//
// To the extent possible under law, Yawning Angel has waived all copyright
// and related or neighboring rights to lioness, using the Creative
// Commons "CC0" public domain dedication. See LICENSE or
// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
package lioness
import (
"errors"
"git.schwanenlied.me/yawning/chacha20.git"
"github.com/minio/blake2b-simd"
)
const (
// KeySize is the key size in bytes.
KeySize = 128
// IVSize is the initialization vector size in bytes.
IVSize = 48
// MinBlockSize is the minimum block size in bytes.
MinBlockSize = 32 + 1
// MaxBlockSize is the maximum block size in bytes.
MaxBlockSize = 32 + (64 * (1 << 32))
lSize = chacha20.KeySize
)
var (
// ErrBlockSize is the error returned when the block size is invalid.
ErrBlockSize = errors.New("lioness: invalid block size")
xorBytes32 = xorBytes32Ref
)
// Encrypt encrypts a block. dst and src may overlap.
func Encrypt(key [KeySize]byte, iv [IVSize]byte, dst, src []byte) error {
// XXX: In theory I should enforce MaxBlockSize, but it's > sizeof(int)
// on 32 bit systems.
if len(src) < MinBlockSize || len(dst) < len(src) {
return ErrBlockSize
}
var l [lSize]byte
r := make([]byte, len(dst)-lSize)
var tmp [lSize + IVSize/4]byte
defer zeroBytes(tmp[:])
k1 := key[0:32]
k2 := key[32:64]
k3 := key[64:96]
k4 := key[96:128]
iv1 := iv[0:12]
iv2 := iv[12:24]
iv3 := iv[24:36]
iv4 := iv[36:48]
var s chacha20.Cipher
defer s.Reset()
var hCfg blake2b.Config
hCfg.Size = lSize
hCfg.Key = tmp[:]
// R = ChaCha20(L ^ k1, iv1, R)
xorBytes32(tmp[:lSize], src[0:lSize], k1)
if err := s.ReKey(tmp[:lSize], iv1); err != nil {
return err
}
s.XORKeyStream(r, src[lSize:])
// L = L ^ BLAKE2b(k2 | iv2, R)
copy(tmp[:lSize], k2)
copy(tmp[lSize:], iv2)
h, err := blake2b.New(&hCfg)
if err != nil {
return err
}
defer h.Reset()
h.Write(r)
htmp := h.Sum(nil)
defer zeroBytes(htmp)
xorBytes32(l[:], src[0:lSize], htmp)
// R = ChaCha20(L ^ k3, iv3, R)
xorBytes32(tmp[:lSize], l[:], k3)
if err := s.ReKey(tmp[:lSize], iv3); err != nil {
return err
}
s.XORKeyStream(r, r)
// L ^ BLAKE2b(k4 | iv4, R)
copy(tmp[:lSize], k4)
copy(tmp[lSize:], iv4)
hh, err := blake2b.New(&hCfg) // I wish blake2b-simd supported rekeying.
if err != nil {
return err
}
defer hh.Reset()
hh.Write(r)
htmp = htmp[:0]
htmp = hh.Sum(htmp)
xorBytes32(l[:], l[:], htmp)
copy(dst, l[:])
copy(dst[lSize:], r)
return nil
}
// Decrypt decrypts a block. dst and src may overlap.
func Decrypt(key [KeySize]byte, iv [IVSize]byte, dst, src []byte) error {
// XXX: In theory I should enforce MaxBlockSize, but it's > sizeof(int)
// on 32 bit systems.
if len(src) < MinBlockSize || len(dst) < len(src) {
return ErrBlockSize
}
k1 := key[0:32]
k2 := key[32:64]
k3 := key[64:96]
k4 := key[96:128]
iv1 := iv[0:12]
iv2 := iv[12:24]
iv3 := iv[24:36]
iv4 := iv[36:48]
var l [lSize]byte
r := make([]byte, len(dst)-lSize)
var tmp [lSize + IVSize/4]byte
defer zeroBytes(tmp[:])
var s chacha20.Cipher
defer s.Reset()
var hCfg blake2b.Config
hCfg.Size = lSize
hCfg.Key = tmp[:]
// L = L ^ BLAKE2b(k4 | iv4, R)
copy(tmp[:lSize], k4)
copy(tmp[lSize:], iv4)
h, err := blake2b.New(&hCfg)
if err != nil {
return err
}
defer h.Reset()
h.Write(src[lSize:])
htmp := h.Sum(nil)
defer zeroBytes(htmp)
xorBytes32(l[:], src[0:lSize], htmp)
// R = ChaCha20(L ^ k3, iv3, R)
xorBytes32(tmp[:lSize], l[:], k3)
if err := s.ReKey(tmp[:lSize], iv3); err != nil {
return err
}
s.XORKeyStream(r, src[lSize:])
// L = L ^ BLAKE2b(k2 | iv2, R)
copy(tmp[:lSize], k2)
copy(tmp[lSize:], iv2)
hh, err := blake2b.New(&hCfg) // I wish blake2b-simd supported rekeying.
if err != nil {
return err
}
defer hh.Reset()
hh.Write(r)
htmp = htmp[:0]
htmp = hh.Sum(htmp)
xorBytes32(l[:], l[:], htmp)
// R = ChaCha20(L ^ k1, iv1, R)
xorBytes32(tmp[:lSize], l[:], k1)
if err := s.ReKey(tmp[:lSize], iv1); err != nil {
return err
}
s.XORKeyStream(r, r)
copy(dst, l[:])
copy(dst[lSize:], r)
return nil
}
func xorBytes32Ref(dst, a, b []byte) {
// Note: Before you freak the fuck out and try to optimize this,
// for more platforms, take note that it's 32 bytes. Performance
// here is only meaningful for extremely small messages.
if len(dst) != 32 {
panic("lioness: xorBytes32Ref() len != 32")
}
for i, v := range a {
dst[i] = v ^ b[i]
}
}
func zeroBytes(a []byte) {
// Note: Before you freak the fuck out and try to optimize this,
// the compiler has a special case for it.
//
// See: https://github.com/golang/go/issues/5373
for i := range a {
a[i] = 0
}
}