1 | /*
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2 | * Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
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3 | *
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4 | * Licensed under the OpenSSL license (the "License"). You may not use
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5 | * this file except in compliance with the License. You can obtain a copy
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6 | * in the file LICENSE in the source distribution or at
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7 | * https://www.openssl.org/source/license.html
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8 | */
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9 |
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10 | #include <openssl/crypto.h>
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11 | #include "modes_lcl.h"
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12 | #include <string.h>
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13 |
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14 | /*
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15 | * The input and output encrypted as though 128bit cfb mode is being used.
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16 | * The extra state information to record how much of the 128bit block we have
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17 | * used is contained in *num;
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18 | */
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19 | void CRYPTO_cfb128_encrypt(const unsigned char *in, unsigned char *out,
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20 | size_t len, const void *key,
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21 | unsigned char ivec[16], int *num,
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22 | int enc, block128_f block)
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23 | {
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24 | unsigned int n;
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25 | size_t l = 0;
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26 |
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27 | n = *num;
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28 |
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29 | if (enc) {
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30 | #if !defined(OPENSSL_SMALL_FOOTPRINT)
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31 | if (16 % sizeof(size_t) == 0) { /* always true actually */
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32 | do {
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33 | while (n && len) {
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34 | *(out++) = ivec[n] ^= *(in++);
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35 | --len;
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36 | n = (n + 1) % 16;
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37 | }
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38 | # if defined(STRICT_ALIGNMENT)
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39 | if (((size_t)in | (size_t)out | (size_t)ivec) %
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40 | sizeof(size_t) != 0)
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41 | break;
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42 | # endif
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43 | while (len >= 16) {
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44 | (*block) (ivec, ivec, key);
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45 | for (; n < 16; n += sizeof(size_t)) {
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46 | *(size_t *)(out + n) =
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47 | *(size_t *)(ivec + n) ^= *(size_t *)(in + n);
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48 | }
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49 | len -= 16;
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50 | out += 16;
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51 | in += 16;
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52 | n = 0;
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53 | }
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54 | if (len) {
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55 | (*block) (ivec, ivec, key);
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56 | while (len--) {
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57 | out[n] = ivec[n] ^= in[n];
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58 | ++n;
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59 | }
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60 | }
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61 | *num = n;
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62 | return;
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63 | } while (0);
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64 | }
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65 | /* the rest would be commonly eliminated by x86* compiler */
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66 | #endif
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67 | while (l < len) {
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68 | if (n == 0) {
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69 | (*block) (ivec, ivec, key);
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70 | }
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71 | out[l] = ivec[n] ^= in[l];
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72 | ++l;
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73 | n = (n + 1) % 16;
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74 | }
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75 | *num = n;
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76 | } else {
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77 | #if !defined(OPENSSL_SMALL_FOOTPRINT)
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78 | if (16 % sizeof(size_t) == 0) { /* always true actually */
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79 | do {
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80 | while (n && len) {
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81 | unsigned char c;
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82 | *(out++) = ivec[n] ^ (c = *(in++));
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83 | ivec[n] = c;
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84 | --len;
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85 | n = (n + 1) % 16;
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86 | }
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87 | # if defined(STRICT_ALIGNMENT)
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88 | if (((size_t)in | (size_t)out | (size_t)ivec) %
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89 | sizeof(size_t) != 0)
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90 | break;
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91 | # endif
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92 | while (len >= 16) {
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93 | (*block) (ivec, ivec, key);
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94 | for (; n < 16; n += sizeof(size_t)) {
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95 | size_t t = *(size_t *)(in + n);
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96 | *(size_t *)(out + n) = *(size_t *)(ivec + n) ^ t;
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97 | *(size_t *)(ivec + n) = t;
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98 | }
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99 | len -= 16;
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100 | out += 16;
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101 | in += 16;
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102 | n = 0;
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103 | }
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104 | if (len) {
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105 | (*block) (ivec, ivec, key);
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106 | while (len--) {
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107 | unsigned char c;
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108 | out[n] = ivec[n] ^ (c = in[n]);
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109 | ivec[n] = c;
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110 | ++n;
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111 | }
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112 | }
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113 | *num = n;
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114 | return;
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115 | } while (0);
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116 | }
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117 | /* the rest would be commonly eliminated by x86* compiler */
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118 | #endif
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119 | while (l < len) {
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120 | unsigned char c;
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121 | if (n == 0) {
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122 | (*block) (ivec, ivec, key);
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123 | }
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124 | out[l] = ivec[n] ^ (c = in[l]);
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125 | ivec[n] = c;
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126 | ++l;
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127 | n = (n + 1) % 16;
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128 | }
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129 | *num = n;
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130 | }
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131 | }
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132 |
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133 | /*
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134 | * This expects a single block of size nbits for both in and out. Note that
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135 | * it corrupts any extra bits in the last byte of out
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136 | */
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137 | static void cfbr_encrypt_block(const unsigned char *in, unsigned char *out,
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138 | int nbits, const void *key,
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139 | unsigned char ivec[16], int enc,
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140 | block128_f block)
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141 | {
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142 | int n, rem, num;
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143 | unsigned char ovec[16 * 2 + 1]; /* +1 because we dereference (but don't
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144 | * use) one byte off the end */
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145 |
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146 | if (nbits <= 0 || nbits > 128)
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147 | return;
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148 |
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149 | /* fill in the first half of the new IV with the current IV */
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150 | memcpy(ovec, ivec, 16);
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151 | /* construct the new IV */
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152 | (*block) (ivec, ivec, key);
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153 | num = (nbits + 7) / 8;
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154 | if (enc) /* encrypt the input */
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155 | for (n = 0; n < num; ++n)
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156 | out[n] = (ovec[16 + n] = in[n] ^ ivec[n]);
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157 | else /* decrypt the input */
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158 | for (n = 0; n < num; ++n)
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159 | out[n] = (ovec[16 + n] = in[n]) ^ ivec[n];
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160 | /* shift ovec left... */
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161 | rem = nbits % 8;
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162 | num = nbits / 8;
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163 | if (rem == 0)
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164 | memcpy(ivec, ovec + num, 16);
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165 | else
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166 | for (n = 0; n < 16; ++n)
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167 | ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem);
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168 |
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169 | /* it is not necessary to cleanse ovec, since the IV is not secret */
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170 | }
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171 |
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172 | /* N.B. This expects the input to be packed, MS bit first */
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173 | void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out,
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174 | size_t bits, const void *key,
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175 | unsigned char ivec[16], int *num,
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176 | int enc, block128_f block)
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177 | {
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178 | size_t n;
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179 | unsigned char c[1], d[1];
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180 |
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181 | for (n = 0; n < bits; ++n) {
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182 | c[0] = (in[n / 8] & (1 << (7 - n % 8))) ? 0x80 : 0;
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183 | cfbr_encrypt_block(c, d, 1, key, ivec, enc, block);
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184 | out[n / 8] = (out[n / 8] & ~(1 << (unsigned int)(7 - n % 8))) |
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185 | ((d[0] & 0x80) >> (unsigned int)(n % 8));
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186 | }
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187 | }
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188 |
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189 | void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,
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190 | size_t length, const void *key,
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191 | unsigned char ivec[16], int *num,
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192 | int enc, block128_f block)
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193 | {
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194 | size_t n;
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195 |
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196 | for (n = 0; n < length; ++n)
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197 | cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block);
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198 | }
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