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// Copyright 2009 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.
// The block package 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 block
// A Cipher 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 Cipher interface {
// BlockSize returns the cipher's block size.
BlockSize() int
// Encrypt encrypts the first block in src into dst.
// Src and dst may point at the same memory.
Encrypt(dst, src []byte)
// Decrypt decrypts the first block in src into dst.
// Src and dst may point at the same memory.
Decrypt(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 same(p, q []byte) bool {
if len(p) != len(q) {
return false
}
for i := 0; i < len(p); i++ {
if p[i] != q[i] {
return false
}
}
return true
}
func dup(p []byte) []byte {
q := make([]byte, len(p))
copy(q, p)
return q
}