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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.digest;
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6
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7 import java.security.DigestException;
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8
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9 /**
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10 * HMAC.
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11 *
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12 * @author Christian Plattner
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13 * @version 2.50, 03/15/10
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14 */
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15 public final class HMAC implements Digest {
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16 Digest md;
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17 byte[] k_xor_ipad;
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18 byte[] k_xor_opad;
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19
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20 byte[] tmp;
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21
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22 int size;
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23
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24 public HMAC(Digest md, byte[] key, int size) throws DigestException {
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25 this.md = md;
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26 this.size = size;
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27 tmp = new byte[md.getDigestLength()];
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28 final int BLOCKSIZE = 64;
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29 k_xor_ipad = new byte[BLOCKSIZE];
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30 k_xor_opad = new byte[BLOCKSIZE];
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31
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32 if (key.length > BLOCKSIZE) {
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33 md.reset();
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34 md.update(key);
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35 md.digest(tmp);
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36 key = tmp;
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37 }
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38
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39 System.arraycopy(key, 0, k_xor_ipad, 0, key.length);
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40 System.arraycopy(key, 0, k_xor_opad, 0, key.length);
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41
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42 for (int i = 0; i < BLOCKSIZE; i++) {
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43 k_xor_ipad[i] ^= 0x36;
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44 k_xor_opad[i] ^= 0x5C;
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45 }
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46
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47 md.update(k_xor_ipad);
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48 }
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49
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50 public final int getDigestLength() {
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51 return size;
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52 }
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53
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54 public final void update(byte b) {
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55 md.update(b);
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56 }
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57
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58 public final void update(byte[] b) {
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59 md.update(b);
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60 }
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61
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62 public final void update(byte[] b, int off, int len) {
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63 md.update(b, off, len);
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64 }
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65
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66 public final void reset() {
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67 md.reset();
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68 md.update(k_xor_ipad);
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69 }
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70
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71 public final void digest(byte[] out) throws DigestException {
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72 digest(out, 0);
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73 }
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74
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75 public final void digest(byte[] out, int off) throws DigestException {
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76 md.digest(tmp);
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77 md.update(k_xor_opad);
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78 md.update(tmp);
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79 md.digest(tmp);
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80 System.arraycopy(tmp, 0, out, off, size);
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81 md.update(k_xor_ipad);
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82 }
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83 }
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