1 | /* crypto/bn/bn_exp.c */
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2 | /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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3 | * All rights reserved.
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4 | *
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5 | * This package is an SSL implementation written
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6 | * by Eric Young (eay@cryptsoft.com).
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7 | * The implementation was written so as to conform with Netscapes SSL.
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8 | *
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9 | * This library is free for commercial and non-commercial use as long as
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10 | * the following conditions are aheared to. The following conditions
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11 | * apply to all code found in this distribution, be it the RC4, RSA,
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12 | * lhash, DES, etc., code; not just the SSL code. The SSL documentation
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13 | * included with this distribution is covered by the same copyright terms
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14 | * except that the holder is Tim Hudson (tjh@cryptsoft.com).
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15 | *
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16 | * Copyright remains Eric Young's, and as such any Copyright notices in
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17 | * the code are not to be removed.
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18 | * If this package is used in a product, Eric Young should be given attribution
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19 | * as the author of the parts of the library used.
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20 | * This can be in the form of a textual message at program startup or
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21 | * in documentation (online or textual) provided with the package.
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22 | *
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23 | * Redistribution and use in source and binary forms, with or without
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24 | * modification, are permitted provided that the following conditions
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25 | * are met:
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26 | * 1. Redistributions of source code must retain the copyright
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27 | * notice, this list of conditions and the following disclaimer.
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28 | * 2. Redistributions in binary form must reproduce the above copyright
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29 | * notice, this list of conditions and the following disclaimer in the
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30 | * documentation and/or other materials provided with the distribution.
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31 | * 3. All advertising materials mentioning features or use of this software
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32 | * must display the following acknowledgement:
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33 | * "This product includes cryptographic software written by
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34 | * Eric Young (eay@cryptsoft.com)"
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35 | * The word 'cryptographic' can be left out if the rouines from the library
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36 | * being used are not cryptographic related :-).
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37 | * 4. If you include any Windows specific code (or a derivative thereof) from
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38 | * the apps directory (application code) you must include an acknowledgement:
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39 | * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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40 | *
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41 | * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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42 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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43 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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44 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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45 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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46 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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47 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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48 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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49 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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50 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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51 | * SUCH DAMAGE.
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52 | *
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53 | * The licence and distribution terms for any publically available version or
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54 | * derivative of this code cannot be changed. i.e. this code cannot simply be
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55 | * copied and put under another distribution licence
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56 | * [including the GNU Public Licence.]
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57 | */
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58 | /* ====================================================================
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59 | * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
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60 | *
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61 | * Redistribution and use in source and binary forms, with or without
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62 | * modification, are permitted provided that the following conditions
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63 | * are met:
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64 | *
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65 | * 1. Redistributions of source code must retain the above copyright
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66 | * notice, this list of conditions and the following disclaimer.
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67 | *
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68 | * 2. Redistributions in binary form must reproduce the above copyright
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69 | * notice, this list of conditions and the following disclaimer in
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70 | * the documentation and/or other materials provided with the
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71 | * distribution.
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72 | *
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73 | * 3. All advertising materials mentioning features or use of this
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74 | * software must display the following acknowledgment:
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75 | * "This product includes software developed by the OpenSSL Project
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76 | * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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77 | *
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78 | * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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79 | * endorse or promote products derived from this software without
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80 | * prior written permission. For written permission, please contact
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81 | * openssl-core@openssl.org.
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82 | *
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83 | * 5. Products derived from this software may not be called "OpenSSL"
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84 | * nor may "OpenSSL" appear in their names without prior written
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85 | * permission of the OpenSSL Project.
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86 | *
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87 | * 6. Redistributions of any form whatsoever must retain the following
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88 | * acknowledgment:
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89 | * "This product includes software developed by the OpenSSL Project
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90 | * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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91 | *
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92 | * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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93 | * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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94 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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95 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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96 | * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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97 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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98 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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99 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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100 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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101 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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102 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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103 | * OF THE POSSIBILITY OF SUCH DAMAGE.
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104 | * ====================================================================
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105 | *
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106 | * This product includes cryptographic software written by Eric Young
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107 | * (eay@cryptsoft.com). This product includes software written by Tim
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108 | * Hudson (tjh@cryptsoft.com).
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109 | *
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110 | */
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111 |
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112 |
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113 | #include <stdio.h>
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114 | #include "bn_lcl.h"
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115 |
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116 | #define TABLE_SIZE 32
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117 |
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118 | /* slow but works */
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119 | int BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
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120 | {
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121 | BIGNUM *t;
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122 | int r=0;
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123 |
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124 | bn_check_top(a);
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125 | bn_check_top(b);
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126 | bn_check_top(m);
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127 |
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128 | BN_CTX_start(ctx);
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129 | if ((t = BN_CTX_get(ctx)) == NULL) goto err;
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130 | if (a == b)
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131 | { if (!BN_sqr(t,a,ctx)) goto err; }
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132 | else
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133 | { if (!BN_mul(t,a,b,ctx)) goto err; }
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134 | if (!BN_mod(ret,t,m,ctx)) goto err;
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135 | r=1;
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136 | err:
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137 | BN_CTX_end(ctx);
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138 | return(r);
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139 | }
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140 |
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141 |
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142 | int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
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143 | BN_CTX *ctx)
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144 | {
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145 | int ret;
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146 |
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147 | bn_check_top(a);
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148 | bn_check_top(p);
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149 | bn_check_top(m);
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150 |
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151 | ret=BN_mod_exp_simple(r,a,p,m,ctx);
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152 |
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153 | return(ret);
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154 | }
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155 |
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156 |
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157 |
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158 |
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159 |
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160 | /* The old fallback, simple version :-) */
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161 | int BN_mod_exp_simple(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
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162 | BN_CTX *ctx)
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163 | {
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164 | int i,j,bits,ret=0,wstart,wend,window,wvalue,ts=0;
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165 | int start=1;
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166 | BIGNUM *d;
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167 | BIGNUM val[TABLE_SIZE];
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168 |
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169 | bits=BN_num_bits(p);
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170 |
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171 | if (bits == 0)
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172 | {
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173 | BN_one(r);
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174 | return(1);
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175 | }
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176 |
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177 | BN_CTX_start(ctx);
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178 | if ((d = BN_CTX_get(ctx)) == NULL) goto err;
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179 |
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180 | BN_init(&(val[0]));
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181 | ts=1;
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182 | if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
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183 |
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184 | window = BN_window_bits_for_exponent_size(bits);
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185 | if (window > 1)
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186 | {
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187 | if (!BN_mod_mul(d,&(val[0]),&(val[0]),m,ctx))
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188 | goto err; /* 2 */
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189 | j=1<<(window-1);
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190 | for (i=1; i<j; i++)
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191 | {
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192 | BN_init(&(val[i]));
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193 | if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx))
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194 | goto err;
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195 | }
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196 | ts=i;
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197 | }
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198 |
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199 | start=1; /* This is used to avoid multiplication etc
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200 | * when there is only the value '1' in the
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201 | * buffer. */
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202 | wvalue=0; /* The 'value' of the window */
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203 | wstart=bits-1; /* The top bit of the window */
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204 | wend=0; /* The bottom bit of the window */
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205 |
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206 | if (!BN_one(r)) goto err;
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207 |
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208 | for (;;)
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209 | {
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210 | if (BN_is_bit_set(p,wstart) == 0)
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211 | {
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212 | if (!start)
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213 | if (!BN_mod_mul(r,r,r,m,ctx))
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214 | goto err;
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215 | if (wstart == 0) break;
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216 | wstart--;
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217 | continue;
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218 | }
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219 | /* We now have wstart on a 'set' bit, we now need to work out
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220 | * how bit a window to do. To do this we need to scan
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221 | * forward until the last set bit before the end of the
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222 | * window */
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223 | j=wstart;
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224 | wvalue=1;
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225 | wend=0;
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226 | for (i=1; i<window; i++)
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227 | {
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228 | if (wstart-i < 0) break;
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229 | if (BN_is_bit_set(p,wstart-i))
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230 | {
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231 | wvalue<<=(i-wend);
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232 | wvalue|=1;
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233 | wend=i;
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234 | }
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235 | }
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236 |
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237 | /* wend is the size of the current window */
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238 | j=wend+1;
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239 | /* add the 'bytes above' */
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240 | if (!start)
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241 | for (i=0; i<j; i++)
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242 | {
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243 | if (!BN_mod_mul(r,r,r,m,ctx))
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244 | goto err;
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245 | }
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246 |
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247 | /* wvalue will be an odd number < 2^window */
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248 | if (!BN_mod_mul(r,r,&(val[wvalue>>1]),m,ctx))
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249 | goto err;
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250 |
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251 | /* move the 'window' down further */
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252 | wstart-=wend+1;
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253 | wvalue=0;
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254 | start=0;
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255 | if (wstart < 0) break;
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256 | }
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257 | ret=1;
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258 | err:
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259 | BN_CTX_end(ctx);
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260 | for (i=0; i<ts; i++)
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261 | BN_clear_free(&(val[i]));
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262 | return(ret);
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263 | }
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264 |
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