github.com/peggyl/go@v0.0.0-20151008231540-ae315999c2d5/src/crypto/des/cipher.go (about)

     1  // Copyright 2011 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 des
     6  
     7  import (
     8  	"crypto/cipher"
     9  	"strconv"
    10  )
    11  
    12  // The DES block size in bytes.
    13  const BlockSize = 8
    14  
    15  type KeySizeError int
    16  
    17  func (k KeySizeError) Error() string {
    18  	return "crypto/des: invalid key size " + strconv.Itoa(int(k))
    19  }
    20  
    21  // desCipher is an instance of DES encryption.
    22  type desCipher struct {
    23  	subkeys [16]uint64
    24  }
    25  
    26  // NewCipher creates and returns a new cipher.Block.
    27  func NewCipher(key []byte) (cipher.Block, error) {
    28  	if len(key) != 8 {
    29  		return nil, KeySizeError(len(key))
    30  	}
    31  
    32  	c := new(desCipher)
    33  	c.generateSubkeys(key)
    34  	return c, nil
    35  }
    36  
    37  func (c *desCipher) BlockSize() int { return BlockSize }
    38  
    39  func (c *desCipher) Encrypt(dst, src []byte) { encryptBlock(c.subkeys[:], dst, src) }
    40  
    41  func (c *desCipher) Decrypt(dst, src []byte) { decryptBlock(c.subkeys[:], dst, src) }
    42  
    43  // A tripleDESCipher is an instance of TripleDES encryption.
    44  type tripleDESCipher struct {
    45  	cipher1, cipher2, cipher3 desCipher
    46  }
    47  
    48  // NewTripleDESCipher creates and returns a new cipher.Block.
    49  func NewTripleDESCipher(key []byte) (cipher.Block, error) {
    50  	if len(key) != 24 {
    51  		return nil, KeySizeError(len(key))
    52  	}
    53  
    54  	c := new(tripleDESCipher)
    55  	c.cipher1.generateSubkeys(key[:8])
    56  	c.cipher2.generateSubkeys(key[8:16])
    57  	c.cipher3.generateSubkeys(key[16:])
    58  	return c, nil
    59  }
    60  
    61  func (c *tripleDESCipher) BlockSize() int { return BlockSize }
    62  
    63  func (c *tripleDESCipher) Encrypt(dst, src []byte) {
    64  	c.cipher1.Encrypt(dst, src)
    65  	c.cipher2.Decrypt(dst, dst)
    66  	c.cipher3.Encrypt(dst, dst)
    67  }
    68  
    69  func (c *tripleDESCipher) Decrypt(dst, src []byte) {
    70  	c.cipher3.Decrypt(dst, src)
    71  	c.cipher2.Encrypt(dst, dst)
    72  	c.cipher1.Decrypt(dst, dst)
    73  }