Initial implementation of xchacha20poly1035 aead

xchacha20poly1035/xchachapoly.go

@@ -0,0 +1,237 @@
+package xchacha20poly1305
+
+import (
+	"crypto/cipher"
+	"encoding/binary"
+	"errors"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+var sigma = [4]uint32{0x61707865, 0x3320646e, 0x79622d32, 0x6b206574}
+
+type xchacha20poly1305 struct {
+	key [KeySize]byte
+}
+
+const (
+	// KeySize is the size of the key used by this AEAD, in bytes.
+	KeySize = 32
+	// NonceSize is the size of the nonce used with this AEAD, in bytes.
+	NonceSize = 24
+)
+
+//New xChaChapoly1305 AEAD with 24 byte nonces
+func New(key []byte) (cipher.AEAD, error) {
+	if len(key) != KeySize {
+		return nil, errors.New("chacha20poly1305: bad key length")
+	}
+	ret := new(xchacha20poly1305)
+	copy(ret.key[:], key)
+	return ret, nil
+
+}
+func (c *xchacha20poly1305) NonceSize() int {
+	return NonceSize
+}
+
+func (c *xchacha20poly1305) Overhead() int {
+	return 16
+}
+
+func (c *xchacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
+	if len(nonce) != NonceSize {
+		panic("chacha20poly1305: bad nonce length passed to Seal")
+	}
+
+	if uint64(len(plaintext)) > (1<<38)-64 {
+		panic("chacha20poly1305: plaintext too large")
+	}
+
+	var subKey [KeySize]byte
+	var hNonce [16]byte
+	var subNonce [chacha20poly1305.NonceSize]byte
+	copy(hNonce[:], nonce[:16])
+
+	HChaCha20(&subKey, &hNonce, &c.key)
+
+	chacha20poly1305, _ := chacha20poly1305.New(subKey[:])
+
+	copy(subNonce[4:], nonce[16:])
+
+	return chacha20poly1305.Seal(dst, subNonce[:], plaintext, additionalData)
+}
+
+func (c *xchacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
+	if len(nonce) != NonceSize {
+		panic("chacha20poly1305: bad nonce length passed to Open")
+	}
+	if uint64(len(ciphertext)) > (1<<38)-48 {
+		panic("chacha20poly1305: ciphertext too large")
+	}
+	var subKey [KeySize]byte
+	var hNonce [16]byte
+	var subNonce [chacha20poly1305.NonceSize]byte
+	copy(hNonce[:], nonce[:16])
+
+	HChaCha20(&subKey, &hNonce, &c.key)
+
+	chacha20poly1305, _ := chacha20poly1305.New(subKey[:])
+
+	copy(subNonce[4:], nonce[16:])
+
+	return chacha20poly1305.Open(dst, subNonce[:], ciphertext, additionalData)
+}
+
+// The MIT License (MIT)
+
+// Copyright (c) 2016 Andreas Auernhammer
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// HChaCha20 generates 32 pseudo-random bytes from a 128 bit nonce and a 256 bit secret key.
+// It can be used as a key-derivation-function (KDF).
+func HChaCha20(out *[32]byte, nonce *[16]byte, key *[32]byte) { hChaCha20Generic(out, nonce, key) }
+
+func hChaCha20Generic(out *[32]byte, nonce *[16]byte, key *[32]byte) {
+	v00 := sigma[0]
+	v01 := sigma[1]
+	v02 := sigma[2]
+	v03 := sigma[3]
+	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)
+}