cipher.go

Documentation: crypto/aes

     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  }
    72
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