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jeremybenn |
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package des
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import "strconv"
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// The DES block size in bytes.
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const BlockSize = 8
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type KeySizeError int
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func (k KeySizeError) Error() string {
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return "crypto/des: invalid key size " + strconv.Itoa(int(k))
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}
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// Cipher is an instance of DES encryption.
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type Cipher struct {
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subkeys [16]uint64
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}
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// NewCipher creates and returns a new Cipher.
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func NewCipher(key []byte) (*Cipher, error) {
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if len(key) != 8 {
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return nil, KeySizeError(len(key))
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}
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c := new(Cipher)
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c.generateSubkeys(key)
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return c, nil
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}
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// BlockSize returns the DES block size, 8 bytes.
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func (c *Cipher) BlockSize() int { return BlockSize }
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// Encrypt encrypts the 8-byte buffer src and stores the result in dst.
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// Note that for amounts of data larger than a block,
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// it is not safe to just call Encrypt on successive blocks;
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// instead, use an encryption mode like CBC (see crypto/cipher/cbc.go).
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func (c *Cipher) Encrypt(dst, src []byte) { encryptBlock(c.subkeys[:], dst, src) }
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// Decrypt decrypts the 8-byte buffer src and stores the result in dst.
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func (c *Cipher) Decrypt(dst, src []byte) { decryptBlock(c.subkeys[:], dst, src) }
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// Reset zeros the key data, so that it will no longer
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// appear in the process's memory.
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func (c *Cipher) Reset() {
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for i := 0; i < len(c.subkeys); i++ {
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c.subkeys[i] = 0
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}
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}
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// A TripleDESCipher is an instance of TripleDES encryption.
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type TripleDESCipher struct {
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cipher1, cipher2, cipher3 Cipher
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}
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// NewCipher creates and returns a new Cipher.
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func NewTripleDESCipher(key []byte) (*TripleDESCipher, error) {
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if len(key) != 24 {
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return nil, KeySizeError(len(key))
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}
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c := new(TripleDESCipher)
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c.cipher1.generateSubkeys(key[:8])
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c.cipher2.generateSubkeys(key[8:16])
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c.cipher3.generateSubkeys(key[16:])
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return c, nil
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}
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// BlockSize returns the TripleDES block size, 8 bytes.
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// It is necessary to satisfy the Block interface in the
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// package "crypto/cipher".
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func (c *TripleDESCipher) BlockSize() int { return BlockSize }
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// Encrypts the 8-byte buffer src and stores the result in dst.
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// Note that for amounts of data larger than a block,
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// it is not safe to just call Encrypt on successive blocks;
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// instead, use an encryption mode like CBC (see crypto/cipher/cbc.go).
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func (c *TripleDESCipher) Encrypt(dst, src []byte) {
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c.cipher1.Encrypt(dst, src)
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c.cipher2.Decrypt(dst, dst)
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c.cipher3.Encrypt(dst, dst)
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}
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// Decrypts the 8-byte buffer src and stores the result in dst.
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func (c *TripleDESCipher) Decrypt(dst, src []byte) {
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c.cipher3.Decrypt(dst, src)
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c.cipher2.Encrypt(dst, dst)
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c.cipher1.Decrypt(dst, dst)
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}
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// Reset zeros the key data, so that it will no longer
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// appear in the process's memory.
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func (c *TripleDESCipher) Reset() {
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c.cipher1.Reset()
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c.cipher2.Reset()
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c.cipher3.Reset()
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}
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