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// Copyright (c) 2016 Andreas Auernhammer. All rights reserved.
// Use of this source code is governed by a license that can be
// found in the LICENSE file.
package xchacha20poly1305
import (
"encoding/binary"
"golang.org/x/crypto/chacha20poly1305"
)
func hChaCha20(out *[32]byte, nonce []byte, key *[32]byte) {
v00 := uint32(0x61707865)
v01 := uint32(0x3320646e)
v02 := uint32(0x79622d32)
v03 := uint32(0x6b206574)
v04 := binary.LittleEndian.Uint32(key[0:])
v05 := binary.LittleEndian.Uint32(key[4:])
v06 := binary.LittleEndian.Uint32(key[8:])
v07 := binary.LittleEndian.Uint32(key[12:])
v08 := binary.LittleEndian.Uint32(key[16:])
v09 := binary.LittleEndian.Uint32(key[20:])
v10 := binary.LittleEndian.Uint32(key[24:])
v11 := binary.LittleEndian.Uint32(key[28:])
v12 := binary.LittleEndian.Uint32(nonce[0:])
v13 := binary.LittleEndian.Uint32(nonce[4:])
v14 := binary.LittleEndian.Uint32(nonce[8:])
v15 := binary.LittleEndian.Uint32(nonce[12:])
for i := 0; i < 20; i += 2 {
v00 += v04
v12 ^= v00
v12 = (v12 << 16) | (v12 >> 16)
v08 += v12
v04 ^= v08
v04 = (v04 << 12) | (v04 >> 20)
v00 += v04
v12 ^= v00
v12 = (v12 << 8) | (v12 >> 24)
v08 += v12
v04 ^= v08
v04 = (v04 << 7) | (v04 >> 25)
v01 += v05
v13 ^= v01
v13 = (v13 << 16) | (v13 >> 16)
v09 += v13
v05 ^= v09
v05 = (v05 << 12) | (v05 >> 20)
v01 += v05
v13 ^= v01
v13 = (v13 << 8) | (v13 >> 24)
v09 += v13
v05 ^= v09
v05 = (v05 << 7) | (v05 >> 25)
v02 += v06
v14 ^= v02
v14 = (v14 << 16) | (v14 >> 16)
v10 += v14
v06 ^= v10
v06 = (v06 << 12) | (v06 >> 20)
v02 += v06
v14 ^= v02
v14 = (v14 << 8) | (v14 >> 24)
v10 += v14
v06 ^= v10
v06 = (v06 << 7) | (v06 >> 25)
v03 += v07
v15 ^= v03
v15 = (v15 << 16) | (v15 >> 16)
v11 += v15
v07 ^= v11
v07 = (v07 << 12) | (v07 >> 20)
v03 += v07
v15 ^= v03
v15 = (v15 << 8) | (v15 >> 24)
v11 += v15
v07 ^= v11
v07 = (v07 << 7) | (v07 >> 25)
v00 += v05
v15 ^= v00
v15 = (v15 << 16) | (v15 >> 16)
v10 += v15
v05 ^= v10
v05 = (v05 << 12) | (v05 >> 20)
v00 += v05
v15 ^= v00
v15 = (v15 << 8) | (v15 >> 24)
v10 += v15
v05 ^= v10
v05 = (v05 << 7) | (v05 >> 25)
v01 += v06
v12 ^= v01
v12 = (v12 << 16) | (v12 >> 16)
v11 += v12
v06 ^= v11
v06 = (v06 << 12) | (v06 >> 20)
v01 += v06
v12 ^= v01
v12 = (v12 << 8) | (v12 >> 24)
v11 += v12
v06 ^= v11
v06 = (v06 << 7) | (v06 >> 25)
v02 += v07
v13 ^= v02
v13 = (v13 << 16) | (v13 >> 16)
v08 += v13
v07 ^= v08
v07 = (v07 << 12) | (v07 >> 20)
v02 += v07
v13 ^= v02
v13 = (v13 << 8) | (v13 >> 24)
v08 += v13
v07 ^= v08
v07 = (v07 << 7) | (v07 >> 25)
v03 += v04
v14 ^= v03
v14 = (v14 << 16) | (v14 >> 16)
v09 += v14
v04 ^= v09
v04 = (v04 << 12) | (v04 >> 20)
v03 += v04
v14 ^= v03
v14 = (v14 << 8) | (v14 >> 24)
v09 += v14
v04 ^= v09
v04 = (v04 << 7) | (v04 >> 25)
}
binary.LittleEndian.PutUint32(out[0:], v00)
binary.LittleEndian.PutUint32(out[4:], v01)
binary.LittleEndian.PutUint32(out[8:], v02)
binary.LittleEndian.PutUint32(out[12:], v03)
binary.LittleEndian.PutUint32(out[16:], v12)
binary.LittleEndian.PutUint32(out[20:], v13)
binary.LittleEndian.PutUint32(out[24:], v14)
binary.LittleEndian.PutUint32(out[28:], v15)
}
func Encrypt(
dst []byte,
nonceFull *[24]byte,
plaintext []byte,
additionalData []byte,
key *[chacha20poly1305.KeySize]byte,
) []byte {
var nonce [chacha20poly1305.NonceSize]byte
var derivedKey [chacha20poly1305.KeySize]byte
hChaCha20(&derivedKey, nonceFull[:16], key)
aead, _ := chacha20poly1305.New(derivedKey[:])
copy(nonce[4:], nonceFull[16:])
return aead.Seal(dst, nonce[:], plaintext, additionalData)
}
func Decrypt(
dst []byte,
nonceFull *[24]byte,
plaintext []byte,
additionalData []byte,
key *[chacha20poly1305.KeySize]byte,
) ([]byte, error) {
var nonce [chacha20poly1305.NonceSize]byte
var derivedKey [chacha20poly1305.KeySize]byte
hChaCha20(&derivedKey, nonceFull[:16], key)
aead, _ := chacha20poly1305.New(derivedKey[:])
copy(nonce[4:], nonceFull[16:])
return aead.Open(dst, nonce[:], plaintext, additionalData)
}
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