mirror of
https://github.com/taigrr/arc
synced 2025-01-18 04:33:13 -08:00
91 lines
1.8 KiB
Go
91 lines
1.8 KiB
Go
// Copyright (C) 2016 - Will Glozer. All rights reserved.
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// Package chacha20poly1305 implements the AEAD_CHACHA20_POLY1305
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// construction as specified in RFC 7539.
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package chacha20poly1305
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import (
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"encoding/binary"
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"schwanenlied.me/yawning/chacha20"
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"schwanenlied.me/yawning/poly1305"
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)
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const (
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KeySize = chacha20.KeySize
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NonceSize = chacha20.INonceSize
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TagSize = poly1305.Size
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)
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var padding [16]byte
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type ChaCha20Poly1305 struct {
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a, n uint64
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chacha20.Cipher
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poly1305.Poly1305
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}
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func New(key *[KeySize]byte, nonce *[NonceSize]byte) *ChaCha20Poly1305 {
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x := &ChaCha20Poly1305{}
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x.Init(key[:], nonce[:])
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return x
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}
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func (x *ChaCha20Poly1305) Init(key, nonce []byte) error {
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err := x.ReKey(key, nonce)
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if err == nil {
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x.initPoly1305()
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x.Seek(1)
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x.a = 0
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x.n = 0
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}
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return err
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}
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func (x *ChaCha20Poly1305) Auth(src []byte) {
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if n := len(src); n > 0 {
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x.Poly1305.Write(src)
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x.a = uint64(n)
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x.Poly1305.Write(padding[:16-n%16])
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}
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}
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func (x *ChaCha20Poly1305) Decrypt(dst, src []byte) {
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x.Poly1305.Write(src)
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x.XORKeyStream(dst, src)
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x.n += uint64(len(src))
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}
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func (x *ChaCha20Poly1305) Encrypt(dst, src []byte) {
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n := len(src)
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x.XORKeyStream(dst, src)
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x.Poly1305.Write(dst[:n])
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x.n += uint64(n)
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}
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func (x *ChaCha20Poly1305) Tag(b []byte) []byte {
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var lengths [16]byte
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binary.LittleEndian.PutUint64(lengths[0:], uint64(x.a))
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binary.LittleEndian.PutUint64(lengths[8:], uint64(x.n))
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x.Poly1305.Write(padding[:16-x.n%16])
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x.Poly1305.Write(lengths[:])
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return x.Poly1305.Sum(b)
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}
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func (x *ChaCha20Poly1305) Reset() {
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x.Cipher.Reset()
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}
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func (x *ChaCha20Poly1305) TagSize() int {
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return TagSize
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}
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func (x *ChaCha20Poly1305) initPoly1305() {
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var key [poly1305.KeySize]byte
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x.KeyStream(key[:])
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x.Poly1305.Init(key[:])
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for i := range key {
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key[i] = 0
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}
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}
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