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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package cipher implements standard block cipher modes that can be wrapped
// around low-level block cipher implementations.
// See http://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html
// and NIST Special Publication 800-38A.
package cipher
// A Block represents an implementation of block cipher
// using a given key. It provides the capability to encrypt
// or decrypt individual blocks. The mode implementations
// extend that capability to streams of blocks.
type Block interface {
// BlockSize returns the cipher's block size.
BlockSize() int
// Encrypt encrypts the first block in src into dst.
// Dst and src may point at the same memory.
Encrypt(dst, src []byte)
// Decrypt decrypts the first block in src into dst.
// Dst and src may point at the same memory.
Decrypt(dst, src []byte)
}
// A Stream represents a stream cipher.
type Stream interface {
// XORKeyStream XORs each byte in the given slice with a byte from the
// cipher's key stream. Dst and src may point to the same memory.
XORKeyStream(dst, src []byte)
}
// A BlockMode represents a block cipher running in a block-based mode (CBC,
// ECB etc).
type BlockMode interface {
// BlockSize returns the mode's block size.
BlockSize() int
// CryptBlocks encrypts or decrypts a number of blocks. The length of
// src must be a multiple of the block size. Dst and src may point to
// the same memory.
CryptBlocks(dst, src []byte)
}
// Utility routines
func shift1(dst, src []byte) byte {
var b byte
for i := len(src) - 1; i >= 0; i-- {
bb := src[i] >> 7
dst[i] = src[i]<<1 | b
b = bb
}
return b
}
func dup(p []byte) []byte {
q := make([]byte, len(p))
copy(q, p)
return q
}
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