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comparison src/com/trilead/ssh2/crypto/cipher/CBCMode.java @ 0:0ce5cc452d02

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initial version
author Carl Byington <carl@five-ten-sg.com>
date Thu, 22 May 2014 10:41:19 -0700
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-1:000000000000 0:0ce5cc452d02
1 package com.trilead.ssh2.crypto.cipher;
2
3 /**
4 * CBCMode.
5 *
6 * @author Christian Plattner, plattner@trilead.com
7 * @version $Id: CBCMode.java,v 1.1 2007/10/15 12:49:55 cplattne Exp $
8 */
9 public class CBCMode implements BlockCipher {
10 BlockCipher tc;
11 int blockSize;
12 boolean doEncrypt;
13
14 byte[] cbc_vector;
15 byte[] tmp_vector;
16
17 public void init(boolean forEncryption, byte[] key) {
18 }
19
20 public CBCMode(BlockCipher tc, byte[] iv, boolean doEncrypt)
21 throws IllegalArgumentException {
22 this.tc = tc;
23 this.blockSize = tc.getBlockSize();
24 this.doEncrypt = doEncrypt;
25
26 if (this.blockSize != iv.length)
27 throw new IllegalArgumentException("IV must be " + blockSize
28 + " bytes long! (currently " + iv.length + ")");
29
30 this.cbc_vector = new byte[blockSize];
31 this.tmp_vector = new byte[blockSize];
32 System.arraycopy(iv, 0, cbc_vector, 0, blockSize);
33 }
34
35 public int getBlockSize() {
36 return blockSize;
37 }
38
39 private void encryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff) {
40 for (int i = 0; i < blockSize; i++)
41 cbc_vector[i] ^= src[srcoff + i];
42
43 tc.transformBlock(cbc_vector, 0, dst, dstoff);
44 System.arraycopy(dst, dstoff, cbc_vector, 0, blockSize);
45 }
46
47 private void decryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff) {
48 /* Assume the worst, src and dst are overlapping... */
49 System.arraycopy(src, srcoff, tmp_vector, 0, blockSize);
50 tc.transformBlock(src, srcoff, dst, dstoff);
51
52 for (int i = 0; i < blockSize; i++)
53 dst[dstoff + i] ^= cbc_vector[i];
54
55 /* ...that is why we need a tmp buffer. */
56 byte[] swap = cbc_vector;
57 cbc_vector = tmp_vector;
58 tmp_vector = swap;
59 }
60
61 public void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff) {
62 if (doEncrypt)
63 encryptBlock(src, srcoff, dst, dstoff);
64 else
65 decryptBlock(src, srcoff, dst, dstoff);
66 }
67 }