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  	"crypto/internal/subtle"
		10  	"encoding/binary"
		11  	"strconv"
		12  )
		13  
		14  // The DES block size in bytes.
		15  const BlockSize = 8
		16  
		17  type KeySizeError int
		18  
		19  func (k KeySizeError) Error() string {
		20  	return "crypto/des: invalid key size " + strconv.Itoa(int(k))
		21  }
		22  
		23  // desCipher is an instance of DES encryption.
		24  type desCipher struct {
		25  	subkeys [16]uint64
		26  }
		27  
		28  // NewCipher creates and returns a new cipher.Block.
		29  func NewCipher(key []byte) (cipher.Block, error) {
		30  	if len(key) != 8 {
		31  		return nil, KeySizeError(len(key))
		32  	}
		33  
		34  	c := new(desCipher)
		35  	c.generateSubkeys(key)
		36  	return c, nil
		37  }
		38  
		39  func (c *desCipher) BlockSize() int { return BlockSize }
		40  
		41  func (c *desCipher) Encrypt(dst, src []byte) {
		42  	if len(src) < BlockSize {
		43  		panic("crypto/des: input not full block")
		44  	}
		45  	if len(dst) < BlockSize {
		46  		panic("crypto/des: output not full block")
		47  	}
		48  	if subtle.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
		49  		panic("crypto/des: invalid buffer overlap")
		50  	}
		51  	encryptBlock(c.subkeys[:], dst, src)
		52  }
		53  
		54  func (c *desCipher) Decrypt(dst, src []byte) {
		55  	if len(src) < BlockSize {
		56  		panic("crypto/des: input not full block")
		57  	}
		58  	if len(dst) < BlockSize {
		59  		panic("crypto/des: output not full block")
		60  	}
		61  	if subtle.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
		62  		panic("crypto/des: invalid buffer overlap")
		63  	}
		64  	decryptBlock(c.subkeys[:], dst, src)
		65  }
		66  
		67  // A tripleDESCipher is an instance of TripleDES encryption.
		68  type tripleDESCipher struct {
		69  	cipher1, cipher2, cipher3 desCipher
		70  }
		71  
		72  // NewTripleDESCipher creates and returns a new cipher.Block.
		73  func NewTripleDESCipher(key []byte) (cipher.Block, error) {
		74  	if len(key) != 24 {
		75  		return nil, KeySizeError(len(key))
		76  	}
		77  
		78  	c := new(tripleDESCipher)
		79  	c.cipher1.generateSubkeys(key[:8])
		80  	c.cipher2.generateSubkeys(key[8:16])
		81  	c.cipher3.generateSubkeys(key[16:])
		82  	return c, nil
		83  }
		84  
		85  func (c *tripleDESCipher) BlockSize() int { return BlockSize }
		86  
		87  func (c *tripleDESCipher) Encrypt(dst, src []byte) {
		88  	if len(src) < BlockSize {
		89  		panic("crypto/des: input not full block")
		90  	}
		91  	if len(dst) < BlockSize {
		92  		panic("crypto/des: output not full block")
		93  	}
		94  	if subtle.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
		95  		panic("crypto/des: invalid buffer overlap")
		96  	}
		97  
		98  	b := binary.BigEndian.Uint64(src)
		99  	b = permuteInitialBlock(b)
	 100  	left, right := uint32(b>>32), uint32(b)
	 101  
	 102  	left = (left << 1) | (left >> 31)
	 103  	right = (right << 1) | (right >> 31)
	 104  
	 105  	for i := 0; i < 8; i++ {
	 106  		left, right = feistel(left, right, c.cipher1.subkeys[2*i], c.cipher1.subkeys[2*i+1])
	 107  	}
	 108  	for i := 0; i < 8; i++ {
	 109  		right, left = feistel(right, left, c.cipher2.subkeys[15-2*i], c.cipher2.subkeys[15-(2*i+1)])
	 110  	}
	 111  	for i := 0; i < 8; i++ {
	 112  		left, right = feistel(left, right, c.cipher3.subkeys[2*i], c.cipher3.subkeys[2*i+1])
	 113  	}
	 114  
	 115  	left = (left << 31) | (left >> 1)
	 116  	right = (right << 31) | (right >> 1)
	 117  
	 118  	preOutput := (uint64(right) << 32) | uint64(left)
	 119  	binary.BigEndian.PutUint64(dst, permuteFinalBlock(preOutput))
	 120  }
	 121  
	 122  func (c *tripleDESCipher) Decrypt(dst, src []byte) {
	 123  	if len(src) < BlockSize {
	 124  		panic("crypto/des: input not full block")
	 125  	}
	 126  	if len(dst) < BlockSize {
	 127  		panic("crypto/des: output not full block")
	 128  	}
	 129  	if subtle.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
	 130  		panic("crypto/des: invalid buffer overlap")
	 131  	}
	 132  
	 133  	b := binary.BigEndian.Uint64(src)
	 134  	b = permuteInitialBlock(b)
	 135  	left, right := uint32(b>>32), uint32(b)
	 136  
	 137  	left = (left << 1) | (left >> 31)
	 138  	right = (right << 1) | (right >> 31)
	 139  
	 140  	for i := 0; i < 8; i++ {
	 141  		left, right = feistel(left, right, c.cipher3.subkeys[15-2*i], c.cipher3.subkeys[15-(2*i+1)])
	 142  	}
	 143  	for i := 0; i < 8; i++ {
	 144  		right, left = feistel(right, left, c.cipher2.subkeys[2*i], c.cipher2.subkeys[2*i+1])
	 145  	}
	 146  	for i := 0; i < 8; i++ {
	 147  		left, right = feistel(left, right, c.cipher1.subkeys[15-2*i], c.cipher1.subkeys[15-(2*i+1)])
	 148  	}
	 149  
	 150  	left = (left << 31) | (left >> 1)
	 151  	right = (right << 31) | (right >> 1)
	 152  
	 153  	preOutput := (uint64(right) << 32) | uint64(left)
	 154  	binary.BigEndian.PutUint64(dst, permuteFinalBlock(preOutput))
	 155  }
	 156
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