libgo/go/crypto/aes/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 package aes
   6
   7 import (
   8         "crypto/cipher"
   9         "strconv"
  10 )
  11
  12 // The AES block size in bytes.
  13 const BlockSize = 16
  14
  15 // A cipher is an instance of AES encryption using a particular key.
  16 type aesCipher struct {
  17         enc []uint32
  18         dec []uint32
  19 }
  20
  21 type KeySizeError int
  22
  23 func (k KeySizeError) Error() string {
  24         return "crypto/aes: invalid key size " + strconv.Itoa(int(k))
  25 }
  26
  27 // NewCipher creates and returns a new cipher.Block.
  28 // The key argument should be the AES key,
  29 // either 16, 24, or 32 bytes to select
  30 // AES-128, AES-192, or AES-256.
  31 func NewCipher(key []byte) (cipher.Block, error) {
  32         k := len(key)
  33         switch k {
  34         default:
  35                 return nil, KeySizeError(k)
  36         case 16, 24, 32:
  37                 break
  38         }
  39         return newCipher(key)
  40 }
  41
  42 // newCipherGeneric creates and returns a new cipher.Block
  43 // implemented in pure Go.
  44 func newCipherGeneric(key []byte) (cipher.Block, error) {
  45         n := len(key) + 28
  46         c := aesCipher{make([]uint32, n), make([]uint32, n)}
  47         expandKeyGo(key, c.enc, c.dec)
  48         return &c, nil
  49 }
  50
  51 func (c *aesCipher) BlockSize() int { return BlockSize }
  52
  53 func (c *aesCipher) Encrypt(dst, src []byte) {
  54         if len(src) < BlockSize {
  55                 panic("crypto/aes: input not full block")
  56         }
  57         if len(dst) < BlockSize {
  58                 panic("crypto/aes: output not full block")
  59         }
  60         encryptBlockGo(c.enc, dst, src)
  61 }
  62
  63 func (c *aesCipher) Decrypt(dst, src []byte) {
  64         if len(src) < BlockSize {
  65                 panic("crypto/aes: input not full block")
  66         }
  67         if len(dst) < BlockSize {
  68                 panic("crypto/aes: output not full block")
  69         }
  70         decryptBlockGo(c.dec, dst, src)
  71 }