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annotate src/ch/ethz/ssh2/crypto/cipher/CBCMode.java @ 435:9c6a269fabb5 stable-1.9.2
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| author | Carl Byington <carl@five-ten-sg.com> |
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| date | Thu, 09 Apr 2015 11:32:38 -0700 |
| parents | 071eccdff8ea |
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| rev | line source |
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1 /* |
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2 * Copyright (c) 2006-2011 Christian Plattner. All rights reserved. |
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3 * Please refer to the LICENSE.txt for licensing details. |
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4 */ |
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5 package ch.ethz.ssh2.crypto.cipher; |
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6 |
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7 /** |
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8 * CBCMode. |
| 307 | 9 * |
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10 * @author Christian Plattner |
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11 * @version 2.50, 03/15/10 |
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12 */ |
| 307 | 13 public class CBCMode implements BlockCipher { |
| 14 BlockCipher tc; | |
| 15 int blockSize; | |
| 16 boolean doEncrypt; | |
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17 |
| 307 | 18 byte[] cbc_vector; |
| 19 byte[] tmp_vector; | |
| 20 | |
| 21 public void init(boolean forEncryption, byte[] key) { | |
| 22 } | |
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23 |
| 307 | 24 public CBCMode(BlockCipher tc, byte[] iv, boolean doEncrypt) |
| 25 throws IllegalArgumentException { | |
| 26 this.tc = tc; | |
| 27 this.blockSize = tc.getBlockSize(); | |
| 28 this.doEncrypt = doEncrypt; | |
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29 |
| 307 | 30 if (this.blockSize != iv.length) |
| 31 throw new IllegalArgumentException("IV must be " + blockSize | |
| 32 + " bytes long! (currently " + iv.length + ")"); | |
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33 |
| 307 | 34 this.cbc_vector = new byte[blockSize]; |
| 35 this.tmp_vector = new byte[blockSize]; | |
| 36 System.arraycopy(iv, 0, cbc_vector, 0, blockSize); | |
| 37 } | |
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38 |
| 307 | 39 public int getBlockSize() { |
| 40 return blockSize; | |
| 41 } | |
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42 |
| 307 | 43 private void encryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff) { |
| 44 for (int i = 0; i < blockSize; i++) | |
| 45 cbc_vector[i] ^= src[srcoff + i]; | |
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46 |
| 307 | 47 tc.transformBlock(cbc_vector, 0, dst, dstoff); |
| 48 System.arraycopy(dst, dstoff, cbc_vector, 0, blockSize); | |
| 49 } | |
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50 |
| 307 | 51 private void decryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff) { |
| 52 /* Assume the worst, src and dst are overlapping... */ | |
| 53 System.arraycopy(src, srcoff, tmp_vector, 0, blockSize); | |
| 54 tc.transformBlock(src, srcoff, dst, dstoff); | |
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55 |
| 307 | 56 for (int i = 0; i < blockSize; i++) |
| 57 dst[dstoff + i] ^= cbc_vector[i]; | |
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58 |
| 307 | 59 /* ...that is why we need a tmp buffer. */ |
| 60 byte[] swap = cbc_vector; | |
| 61 cbc_vector = tmp_vector; | |
| 62 tmp_vector = swap; | |
| 63 } | |
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64 |
| 307 | 65 public void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff) { |
| 66 if (doEncrypt) | |
| 67 encryptBlock(src, srcoff, dst, dstoff); | |
| 68 else | |
| 69 decryptBlock(src, srcoff, dst, dstoff); | |
| 70 } | |
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71 } |