Source file src/pkg/crypto/des/cipher.go

     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	}