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380
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.com |
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10 */ |
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11 |
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12 /* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b |
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13 * |
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14 * All curves taken from NIST recommendation paper of July 1999 |
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15 * Available at http://csrc.nist.gov/cryptval/dss.htm |
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16 */ |
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17 #include "tomcrypt.h" |
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18 |
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19 /** |
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20 @file ltc_ecc_mulmod_timing.c |
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21 ECC Crypto, Tom St Denis |
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22 */ |
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23 |
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24 #ifdef MECC |
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25 |
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26 #ifdef LTC_ECC_TIMING_RESISTANT |
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27 |
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28 /** |
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29 Perform a point multiplication (timing resistant) |
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30 @param k The scalar to multiply by |
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31 @param G The base point |
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32 @param R [out] Destination for kG |
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33 @param modulus The modulus of the field the ECC curve is in |
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34 @param map Boolean whether to map back to affine or not (1==map, 0 == leave in projective) |
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35 @return CRYPT_OK on success |
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36 */ |
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37 int ltc_ecc_mulmod(void *k, ecc_point *G, ecc_point *R, void *modulus, int map) |
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38 { |
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39 ecc_point *tG, *M[3]; |
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40 int i, j, err; |
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41 void *mu, *mp; |
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42 unsigned long buf; |
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43 int first, bitbuf, bitcpy, bitcnt, mode, digidx; |
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44 |
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45 LTC_ARGCHK(k != NULL); |
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46 LTC_ARGCHK(G != NULL); |
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47 LTC_ARGCHK(R != NULL); |
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48 LTC_ARGCHK(modulus != NULL); |
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49 |
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50 /* init montgomery reduction */ |
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51 if ((err = mp_montgomery_setup(modulus, &mp)) != CRYPT_OK) { |
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52 return err; |
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53 } |
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54 if ((err = mp_init(&mu)) != CRYPT_OK) { |
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55 mp_montgomery_free(mp); |
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56 return err; |
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57 } |
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58 if ((err = mp_montgomery_normalization(mu, modulus)) != CRYPT_OK) { |
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59 mp_clear(mu); |
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60 mp_montgomery_free(mp); |
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61 return err; |
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62 } |
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63 |
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64 /* alloc ram for window temps */ |
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65 for (i = 0; i < 3; i++) { |
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66 M[i] = ltc_ecc_new_point(); |
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67 if (M[i] == NULL) { |
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68 for (j = 0; j < i; j++) { |
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69 ltc_ecc_del_point(M[j]); |
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70 } |
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71 mp_clear(mu); |
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72 mp_montgomery_free(mp); |
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73 return CRYPT_MEM; |
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74 } |
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75 } |
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76 |
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77 /* make a copy of G incase R==G */ |
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78 tG = ltc_ecc_new_point(); |
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79 if (tG == NULL) { err = CRYPT_MEM; goto done; } |
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80 |
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81 /* tG = G and convert to montgomery */ |
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82 if ((err = mp_mulmod(G->x, mu, modulus, tG->x)) != CRYPT_OK) { goto done; } |
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83 if ((err = mp_mulmod(G->y, mu, modulus, tG->y)) != CRYPT_OK) { goto done; } |
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84 if ((err = mp_mulmod(G->z, mu, modulus, tG->z)) != CRYPT_OK) { goto done; } |
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85 mp_clear(mu); |
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86 mu = NULL; |
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87 |
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88 /* calc the M tab */ |
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89 /* M[0] == G */ |
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90 if ((err = mp_copy(tG->x, M[0]->x)) != CRYPT_OK) { goto done; } |
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91 if ((err = mp_copy(tG->y, M[0]->y)) != CRYPT_OK) { goto done; } |
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92 if ((err = mp_copy(tG->z, M[0]->z)) != CRYPT_OK) { goto done; } |
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93 /* M[1] == 2G */ |
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94 if ((err = ltc_mp.ecc_ptdbl(tG, M[1], modulus, mp)) != CRYPT_OK) { goto done; } |
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95 |
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96 /* setup sliding window */ |
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97 mode = 0; |
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98 bitcnt = 1; |
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99 buf = 0; |
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100 digidx = mp_get_digit_count(k) - 1; |
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101 bitcpy = bitbuf = 0; |
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102 first = 1; |
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103 |
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104 /* perform ops */ |
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105 for (;;) { |
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106 /* grab next digit as required */ |
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107 if (--bitcnt == 0) { |
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108 if (digidx == -1) { |
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109 break; |
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110 } |
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111 buf = mp_get_digit(k, digidx); |
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112 bitcnt = (int) MP_DIGIT_BIT; |
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113 --digidx; |
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114 } |
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115 |
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116 /* grab the next msb from the ltiplicand */ |
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117 i = (buf >> (MP_DIGIT_BIT - 1)) & 1; |
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118 buf <<= 1; |
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119 |
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120 if (mode == 0 && i == 0) { |
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121 /* dummy operations */ |
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122 if ((err = ltc_mp.ecc_ptadd(M[0], M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } |
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123 if ((err = ltc_mp.ecc_ptdbl(M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } |
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124 continue; |
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125 } |
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126 |
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127 if (mode == 0 && i == 1) { |
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128 mode = 1; |
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129 /* dummy operations */ |
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130 if ((err = ltc_mp.ecc_ptadd(M[0], M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } |
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131 if ((err = ltc_mp.ecc_ptdbl(M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } |
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132 continue; |
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133 } |
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134 |
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135 if ((err = ltc_mp.ecc_ptadd(M[0], M[1], M[i^1], modulus, mp)) != CRYPT_OK) { goto done; } |
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136 if ((err = ltc_mp.ecc_ptdbl(M[i], M[i], modulus, mp)) != CRYPT_OK) { goto done; } |
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137 } |
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138 |
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139 /* copy result out */ |
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140 if ((err = mp_copy(M[0]->x, R->x)) != CRYPT_OK) { goto done; } |
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141 if ((err = mp_copy(M[0]->y, R->y)) != CRYPT_OK) { goto done; } |
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142 if ((err = mp_copy(M[0]->z, R->z)) != CRYPT_OK) { goto done; } |
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143 |
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144 /* map R back from projective space */ |
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145 if (map) { |
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146 err = ltc_ecc_map(R, modulus, mp); |
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147 } else { |
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148 err = CRYPT_OK; |
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149 } |
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150 done: |
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151 if (mu != NULL) { |
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152 mp_clear(mu); |
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153 } |
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154 mp_montgomery_free(mp); |
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155 ltc_ecc_del_point(tG); |
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156 for (i = 0; i < 3; i++) { |
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157 ltc_ecc_del_point(M[i]); |
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158 } |
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159 return err; |
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160 } |
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161 |
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162 #endif |
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163 #endif |
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164 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_mulmod_timing.c,v $ */ |
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165 /* $Revision: 1.11 $ */ |
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166 /* $Date: 2006/12/04 22:17:46 $ */ |
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167 |
