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42 lines
2 KiB
Go
42 lines
2 KiB
Go
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// Copyright (c) 2016 Andreas Auernhammer. All rights reserved.
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// Use of this source code is governed by a license that can be
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// found in the LICENSE file.
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// Package chacha20 implements the ChaCha20 / XChaCha20 stream chipher.
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// Notice that one specific key-nonce combination must be unique for all time.
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//
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// There are three versions of ChaCha20:
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// - ChaCha20 with a 64 bit nonce (en/decrypt up to 2^64 * 64 bytes for one key-nonce combination)
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// - ChaCha20 with a 96 bit nonce (en/decrypt up to 2^32 * 64 bytes (~256 GB) for one key-nonce combination)
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// - XChaCha20 with a 192 bit nonce (en/decrypt up to 2^64 * 64 bytes for one key-nonce combination)
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package chacha20 // import "github.com/aead/chacha20"
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import (
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"crypto/cipher"
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"github.com/aead/chacha20/chacha"
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)
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// XORKeyStream crypts bytes from src to dst using the given nonce and key.
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// The length of the nonce determinds the version of ChaCha20:
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// - 8 bytes: ChaCha20 with a 64 bit nonce and a 2^64 * 64 byte period.
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// - 12 bytes: ChaCha20 as defined in RFC 7539 and a 2^32 * 64 byte period.
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// - 24 bytes: XChaCha20 with a 192 bit nonce and a 2^64 * 64 byte period.
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// Src and dst may be the same slice but otherwise should not overlap.
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// If len(dst) < len(src) this function panics.
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// If the nonce is neither 64, 96 nor 192 bits long, this function panics.
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func XORKeyStream(dst, src, nonce, key []byte) {
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chacha.XORKeyStream(dst, src, nonce, key, 20)
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}
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// NewCipher returns a new cipher.Stream implementing a ChaCha20 version.
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// The nonce must be unique for one key for all time.
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// The length of the nonce determinds the version of ChaCha20:
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// - 8 bytes: ChaCha20 with a 64 bit nonce and a 2^64 * 64 byte period.
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// - 12 bytes: ChaCha20 as defined in RFC 7539 and a 2^32 * 64 byte period.
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// - 24 bytes: XChaCha20 with a 192 bit nonce and a 2^64 * 64 byte period.
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// If the nonce is neither 64, 96 nor 192 bits long, a non-nil error is returned.
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func NewCipher(nonce, key []byte) (cipher.Stream, error) {
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return chacha.NewCipher(nonce, key, 20)
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}
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