Exemplo n.º 1
0
func (n *noise255ctx) mac(keystream, ciphertext, authtext []byte) [16]byte {
	var macKey [32]byte
	var tag [16]byte
	copy(macKey[:], keystream)
	poly1305.Sum(&tag, n.authData(ciphertext, authtext), &macKey)
	return tag
}
Exemplo n.º 2
0
// Seal appends an encrypted and authenticated copy of message to out, which
// must not overlap message. The key and nonce pair must be unique for each
// distinct message and the output will be Overhead bytes longer than message.
func Seal(out, message []byte, nonce *[24]byte, key *[32]byte) []byte {
	var subKey [32]byte
	var counter [16]byte
	setup(&subKey, &counter, nonce, key)

	// The Poly1305 key is generated by encrypting 32 bytes of zeros. Since
	// Salsa20 works with 64-byte blocks, we also generate 32 bytes of
	// keystream as a side effect.
	var firstBlock [64]byte
	salsa.XORKeyStream(firstBlock[:], firstBlock[:], &counter, &subKey)

	var poly1305Key [32]byte
	copy(poly1305Key[:], firstBlock[:])

	out = out[len(out):]
	outLen := len(message) + poly1305.TagSize
	if cap(out) >= outLen {
		out = out[:outLen]
	} else if out == nil {
		out = make([]byte, outLen)
	} else {
		for i := 0; i < outLen; i++ {
			out = append(out, 0)
		}
	}

	// We XOR up to 32 bytes of message with the keystream generated from
	// the first block.
	firstMessageBlock := message
	if len(firstMessageBlock) > 32 {
		firstMessageBlock = firstMessageBlock[:32]
	}

	tagOut := out
	out = out[poly1305.TagSize:]
	for i, x := range firstMessageBlock {
		out[i] = firstBlock[32+i] ^ x
	}
	message = message[len(firstMessageBlock):]
	ciphertext := out
	out = out[len(firstMessageBlock):]

	// Now encrypt the rest.
	counter[8] = 1
	salsa.XORKeyStream(out, message, &counter, &subKey)

	var tag [poly1305.TagSize]byte
	poly1305.Sum(&tag, ciphertext, &poly1305Key)
	copy(tagOut, tag[:])

	return tagOut
}