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4680 | right-hear | 1 | /* This code illustrates a sample implementation |
2 | * of the Arcfour algorithm |
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3 | * Copyright (c) April 29, 1997 Kalle Kaukonen. |
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4 | * All Rights Reserved. |
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5 | * |
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6 | * Redistribution and use in source and binary forms, with or |
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7 | * without modification, are permitted provided that this copyright |
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8 | * notice and disclaimer are retained. |
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9 | * |
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10 | * THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS |
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11 | * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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12 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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13 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KALLE |
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14 | * KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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15 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
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16 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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17 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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18 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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19 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
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20 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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21 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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22 | */ |
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23 | |||
24 | #include "fitz.h" |
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25 | |||
26 | void |
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27 | fz_arc4_init(fz_arc4 *arc4, const unsigned char *key, const unsigned keylen) |
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28 | { |
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29 | unsigned int t, u; |
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30 | unsigned int keyindex; |
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31 | unsigned int stateindex; |
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32 | unsigned char *state; |
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33 | unsigned int counter; |
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34 | |||
35 | state = arc4->state; |
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36 | |||
37 | arc4->x = 0; |
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38 | arc4->y = 0; |
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39 | |||
40 | for (counter = 0; counter < 256; counter++) |
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41 | { |
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42 | state[counter] = counter; |
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43 | } |
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44 | |||
45 | keyindex = 0; |
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46 | stateindex = 0; |
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47 | |||
48 | for (counter = 0; counter < 256; counter++) |
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49 | { |
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50 | t = state[counter]; |
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51 | stateindex = (stateindex + key[keyindex] + t) & 0xff; |
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52 | u = state[stateindex]; |
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53 | |||
54 | state[stateindex] = t; |
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55 | state[counter] = u; |
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56 | |||
57 | if (++keyindex >= keylen) |
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58 | { |
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59 | keyindex = 0; |
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60 | } |
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61 | } |
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62 | } |
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63 | |||
64 | static unsigned char |
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65 | fz_arc4_next(fz_arc4 *arc4) |
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66 | { |
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67 | unsigned int x; |
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68 | unsigned int y; |
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69 | unsigned int sx, sy; |
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70 | unsigned char *state; |
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71 | |||
72 | state = arc4->state; |
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73 | |||
74 | x = (arc4->x + 1) & 0xff; |
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75 | sx = state[x]; |
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76 | y = (sx + arc4->y) & 0xff; |
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77 | sy = state[y]; |
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78 | |||
79 | arc4->x = x; |
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80 | arc4->y = y; |
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81 | |||
82 | state[y] = sx; |
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83 | state[x] = sy; |
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84 | |||
85 | return state[(sx + sy) & 0xff]; |
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86 | } |
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87 | |||
88 | void |
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89 | fz_arc4_encrypt(fz_arc4 *arc4, unsigned char *dest, const unsigned char *src, const unsigned len) |
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90 | { |
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91 | unsigned int i; |
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92 | for (i = 0; i < len; i++) |
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93 | { |
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94 | unsigned char x; |
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95 | x = fz_arc4_next(arc4); |
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96 | dest[i] = src[i] ^ x; |
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97 | } |
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98 | }>>> |