Release v0.3.0

vendor/github.com/aead/chacha20/chacha20.go

@@ -0,0 +1,41 @@
+// 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 chacha20 implements the ChaCha20 / XChaCha20 stream chipher.
+// Notice that one specific key-nonce combination must be unique for all time.
+//
+// There are three versions of ChaCha20:
+// - ChaCha20 with a 64 bit nonce (en/decrypt up to 2^64 * 64 bytes for one key-nonce combination)
+// - ChaCha20 with a 96 bit nonce (en/decrypt up to 2^32 * 64 bytes (~256 GB) for one key-nonce combination)
+// - XChaCha20 with a 192 bit nonce (en/decrypt up to 2^64 * 64 bytes for one key-nonce combination)
+package chacha20 // import "github.com/aead/chacha20"
+
+import (
+	"crypto/cipher"
+
+	"github.com/aead/chacha20/chacha"
+)
+
+// XORKeyStream crypts bytes from src to dst using the given nonce and key.
+// The length of the nonce determinds the version of ChaCha20:
+// - 8 bytes:  ChaCha20 with a 64 bit nonce and a 2^64 * 64 byte period.
+// - 12 bytes: ChaCha20 as defined in RFC 7539 and a 2^32 * 64 byte period.
+// - 24 bytes: XChaCha20 with a 192 bit nonce and a 2^64 * 64 byte period.
+// Src and dst may be the same slice but otherwise should not overlap.
+// If len(dst) < len(src) this function panics.
+// If the nonce is neither 64, 96 nor 192 bits long, this function panics.
+func XORKeyStream(dst, src, nonce, key []byte) {
+	chacha.XORKeyStream(dst, src, nonce, key, 20)
+}
+
+// NewCipher returns a new cipher.Stream implementing a ChaCha20 version.
+// The nonce must be unique for one key for all time.
+// The length of the nonce determinds the version of ChaCha20:
+// - 8 bytes:  ChaCha20 with a 64 bit nonce and a 2^64 * 64 byte period.
+// - 12 bytes: ChaCha20 as defined in RFC 7539 and a 2^32 * 64 byte period.
+// - 24 bytes: XChaCha20 with a 192 bit nonce and a 2^64 * 64 byte period.
+// If the nonce is neither 64, 96 nor 192 bits long, a non-nil error is returned.
+func NewCipher(nonce, key []byte) (cipher.Stream, error) {
+	return chacha.NewCipher(nonce, key, 20)
+}