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Source file src/crypto/des/cipher.go

Documentation: crypto/des

     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  	"encoding/binary"
    10  	"strconv"
    11  )
    12  
    13  // The DES block size in bytes.
    14  const BlockSize = 8
    15  
    16  type KeySizeError int
    17  
    18  func (k KeySizeError) Error() string {
    19  	return "crypto/des: invalid key size " + strconv.Itoa(int(k))
    20  }
    21  
    22  // desCipher is an instance of DES encryption.
    23  type desCipher struct {
    24  	subkeys [16]uint64
    25  }
    26  
    27  // NewCipher creates and returns a new cipher.Block.
    28  func NewCipher(key []byte) (cipher.Block, error) {
    29  	if len(key) != 8 {
    30  		return nil, KeySizeError(len(key))
    31  	}
    32  
    33  	c := new(desCipher)
    34  	c.generateSubkeys(key)
    35  	return c, nil
    36  }
    37  
    38  func (c *desCipher) BlockSize() int { return BlockSize }
    39  
    40  func (c *desCipher) Encrypt(dst, src []byte) { encryptBlock(c.subkeys[:], dst, src) }
    41  
    42  func (c *desCipher) Decrypt(dst, src []byte) { decryptBlock(c.subkeys[:], dst, src) }
    43  
    44  // A tripleDESCipher is an instance of TripleDES encryption.
    45  type tripleDESCipher struct {
    46  	cipher1, cipher2, cipher3 desCipher
    47  }
    48  
    49  // NewTripleDESCipher creates and returns a new cipher.Block.
    50  func NewTripleDESCipher(key []byte) (cipher.Block, error) {
    51  	if len(key) != 24 {
    52  		return nil, KeySizeError(len(key))
    53  	}
    54  
    55  	c := new(tripleDESCipher)
    56  	c.cipher1.generateSubkeys(key[:8])
    57  	c.cipher2.generateSubkeys(key[8:16])
    58  	c.cipher3.generateSubkeys(key[16:])
    59  	return c, nil
    60  }
    61  
    62  func (c *tripleDESCipher) BlockSize() int { return BlockSize }
    63  
    64  func (c *tripleDESCipher) Encrypt(dst, src []byte) {
    65  	b := binary.BigEndian.Uint64(src)
    66  	b = permuteInitialBlock(b)
    67  	left, right := uint32(b>>32), uint32(b)
    68  
    69  	left = (left << 1) | (left >> 31)
    70  	right = (right << 1) | (right >> 31)
    71  
    72  	for i := 0; i < 8; i++ {
    73  		left, right = feistel(left, right, c.cipher1.subkeys[2*i], c.cipher1.subkeys[2*i+1])
    74  	}
    75  	for i := 0; i < 8; i++ {
    76  		right, left = feistel(right, left, c.cipher2.subkeys[15-2*i], c.cipher2.subkeys[15-(2*i+1)])
    77  	}
    78  	for i := 0; i < 8; i++ {
    79  		left, right = feistel(left, right, c.cipher3.subkeys[2*i], c.cipher3.subkeys[2*i+1])
    80  	}
    81  
    82  	left = (left << 31) | (left >> 1)
    83  	right = (right << 31) | (right >> 1)
    84  
    85  	preOutput := (uint64(right) << 32) | uint64(left)
    86  	binary.BigEndian.PutUint64(dst, permuteFinalBlock(preOutput))
    87  }
    88  
    89  func (c *tripleDESCipher) Decrypt(dst, src []byte) {
    90  	b := binary.BigEndian.Uint64(src)
    91  	b = permuteInitialBlock(b)
    92  	left, right := uint32(b>>32), uint32(b)
    93  
    94  	left = (left << 1) | (left >> 31)
    95  	right = (right << 1) | (right >> 31)
    96  
    97  	for i := 0; i < 8; i++ {
    98  		left, right = feistel(left, right, c.cipher3.subkeys[15-2*i], c.cipher3.subkeys[15-(2*i+1)])
    99  	}
   100  	for i := 0; i < 8; i++ {
   101  		right, left = feistel(right, left, c.cipher2.subkeys[2*i], c.cipher2.subkeys[2*i+1])
   102  	}
   103  	for i := 0; i < 8; i++ {
   104  		left, right = feistel(left, right, c.cipher1.subkeys[15-2*i], c.cipher1.subkeys[15-(2*i+1)])
   105  	}
   106  
   107  	left = (left << 31) | (left >> 1)
   108  	right = (right << 31) | (right >> 1)
   109  
   110  	preOutput := (uint64(right) << 32) | uint64(left)
   111  	binary.BigEndian.PutUint64(dst, permuteFinalBlock(preOutput))
   112  }
   113  

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