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comparison src/ch/ethz/ssh2/crypto/cipher/CBCMode.java @ 273:91a31873c42a ganymed

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start conversion from trilead to ganymed
author Carl Byington <carl@five-ten-sg.com>
date Fri, 18 Jul 2014 11:21:46 -0700
parents
children 071eccdff8ea
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272:ce2f4e397703 273:91a31873c42a
1 /*
2 * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
3 * Please refer to the LICENSE.txt for licensing details.
4 */
5 package ch.ethz.ssh2.crypto.cipher;
6
7 /**
8 * CBCMode.
9 *
10 * @author Christian Plattner
11 * @version 2.50, 03/15/10
12 */
13 public class CBCMode implements BlockCipher
14 {
15 BlockCipher tc;
16 int blockSize;
17 boolean doEncrypt;
18
19 byte[] cbc_vector;
20 byte[] tmp_vector;
21
22 public void init(boolean forEncryption, byte[] key)
23 {
24 }
25
26 public CBCMode(BlockCipher tc, byte[] iv, boolean doEncrypt)
27 throws IllegalArgumentException
28 {
29 this.tc = tc;
30 this.blockSize = tc.getBlockSize();
31 this.doEncrypt = doEncrypt;
32
33 if (this.blockSize != iv.length)
34 throw new IllegalArgumentException("IV must be " + blockSize
35 + " bytes long! (currently " + iv.length + ")");
36
37 this.cbc_vector = new byte[blockSize];
38 this.tmp_vector = new byte[blockSize];
39 System.arraycopy(iv, 0, cbc_vector, 0, blockSize);
40 }
41
42 public int getBlockSize()
43 {
44 return blockSize;
45 }
46
47 private void encryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
48 {
49 for (int i = 0; i < blockSize; i++)
50 cbc_vector[i] ^= src[srcoff + i];
51
52 tc.transformBlock(cbc_vector, 0, dst, dstoff);
53
54 System.arraycopy(dst, dstoff, cbc_vector, 0, blockSize);
55 }
56
57 private void decryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
58 {
59 /* Assume the worst, src and dst are overlapping... */
60
61 System.arraycopy(src, srcoff, tmp_vector, 0, blockSize);
62
63 tc.transformBlock(src, srcoff, dst, dstoff);
64
65 for (int i = 0; i < blockSize; i++)
66 dst[dstoff + i] ^= cbc_vector[i];
67
68 /* ...that is why we need a tmp buffer. */
69
70 byte[] swap = cbc_vector;
71 cbc_vector = tmp_vector;
72 tmp_vector = swap;
73 }
74
75 public void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
76 {
77 if (doEncrypt)
78 encryptBlock(src, srcoff, dst, dstoff);
79 else
80 decryptBlock(src, srcoff, dst, dstoff);
81 }
82 }