libgo/go/crypto/block/cipher.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // The block package implements standard block cipher modes
   6 // that can be wrapped around low-level block cipher implementations.
   7 // See http://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html
   8 // and NIST Special Publication 800-38A.
   9 package block
  10
  11 // A Cipher represents an implementation of block cipher
  12 // using a given key.  It provides the capability to encrypt
  13 // or decrypt individual blocks.  The mode implementations
  14 // extend that capability to streams of blocks.
  15 type Cipher interface {
  16         // BlockSize returns the cipher's block size.
  17         BlockSize() int
  18
  19         // Encrypt encrypts the first block in src into dst.
  20         // Src and dst may point at the same memory.
  21         Encrypt(dst, src []byte)
  22
  23         // Decrypt decrypts the first block in src into dst.
  24         // Src and dst may point at the same memory.
  25         Decrypt(dst, src []byte)
  26 }
  27
  28 // Utility routines
  29
  30 func shift1(dst, src []byte) byte {
  31         var b byte
  32         for i := len(src) - 1; i >= 0; i-- {
  33                 bb := src[i] >> 7
  34                 dst[i] = src[i]<<1 | b
  35                 b = bb
  36         }
  37         return b
  38 }
  39
  40 func same(p, q []byte) bool {
  41         if len(p) != len(q) {
  42                 return false
  43         }
  44         for i := 0; i < len(p); i++ {
  45                 if p[i] != q[i] {
  46                         return false
  47                 }
  48         }
  49         return true
  50 }
  51
  52 func dup(p []byte) []byte {
  53         q := make([]byte, len(p))
  54         copy(q, p)
  55         return q
  56 }