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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_projective_dbl_point.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 #if defined(MECC) && (!defined(MECC_ACCEL) || defined(LTM_DESC)) |
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25 |
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26 /** |
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27 Double an ECC point |
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28 @param P The point to double |
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29 @param R [out] The destination of the double |
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30 @param modulus The modulus of the field the ECC curve is in |
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31 @param mp The "b" value from montgomery_setup() |
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32 @return CRYPT_OK on success |
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33 */ |
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34 int ltc_ecc_projective_dbl_point(ecc_point *P, ecc_point *R, void *modulus, void *mp) |
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35 { |
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36 void *t1, *t2; |
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37 int err; |
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38 |
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39 LTC_ARGCHK(P != NULL); |
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40 LTC_ARGCHK(R != NULL); |
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41 LTC_ARGCHK(modulus != NULL); |
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42 LTC_ARGCHK(mp != NULL); |
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43 |
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44 if ((err = mp_init_multi(&t1, &t2, NULL)) != CRYPT_OK) { |
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45 return err; |
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46 } |
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47 |
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48 if (P != R) { |
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49 if ((err = mp_copy(P->x, R->x)) != CRYPT_OK) { goto done; } |
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50 if ((err = mp_copy(P->y, R->y)) != CRYPT_OK) { goto done; } |
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51 if ((err = mp_copy(P->z, R->z)) != CRYPT_OK) { goto done; } |
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52 } |
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53 |
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54 /* t1 = Z * Z */ |
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55 if ((err = mp_sqr(R->z, t1)) != CRYPT_OK) { goto done; } |
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56 if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; } |
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57 /* Z = Y * Z */ |
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58 if ((err = mp_mul(R->z, R->y, R->z)) != CRYPT_OK) { goto done; } |
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59 if ((err = mp_montgomery_reduce(R->z, modulus, mp)) != CRYPT_OK) { goto done; } |
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60 /* Z = 2Z */ |
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61 if ((err = mp_add(R->z, R->z, R->z)) != CRYPT_OK) { goto done; } |
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62 if (mp_cmp(R->z, modulus) != LTC_MP_LT) { |
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63 if ((err = mp_sub(R->z, modulus, R->z)) != CRYPT_OK) { goto done; } |
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64 } |
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65 |
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66 /* T2 = X - T1 */ |
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67 if ((err = mp_sub(R->x, t1, t2)) != CRYPT_OK) { goto done; } |
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68 if (mp_cmp_d(t2, 0) == LTC_MP_LT) { |
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69 if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK) { goto done; } |
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70 } |
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71 /* T1 = X + T1 */ |
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72 if ((err = mp_add(t1, R->x, t1)) != CRYPT_OK) { goto done; } |
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73 if (mp_cmp(t1, modulus) != LTC_MP_LT) { |
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74 if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; } |
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75 } |
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76 /* T2 = T1 * T2 */ |
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77 if ((err = mp_mul(t1, t2, t2)) != CRYPT_OK) { goto done; } |
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78 if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; } |
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79 /* T1 = 2T2 */ |
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80 if ((err = mp_add(t2, t2, t1)) != CRYPT_OK) { goto done; } |
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81 if (mp_cmp(t1, modulus) != LTC_MP_LT) { |
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82 if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; } |
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83 } |
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84 /* T1 = T1 + T2 */ |
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85 if ((err = mp_add(t1, t2, t1)) != CRYPT_OK) { goto done; } |
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86 if (mp_cmp(t1, modulus) != LTC_MP_LT) { |
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87 if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; } |
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88 } |
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89 |
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90 /* Y = 2Y */ |
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91 if ((err = mp_add(R->y, R->y, R->y)) != CRYPT_OK) { goto done; } |
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92 if (mp_cmp(R->y, modulus) != LTC_MP_LT) { |
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93 if ((err = mp_sub(R->y, modulus, R->y)) != CRYPT_OK) { goto done; } |
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94 } |
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95 /* Y = Y * Y */ |
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96 if ((err = mp_sqr(R->y, R->y)) != CRYPT_OK) { goto done; } |
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97 if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK) { goto done; } |
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98 /* T2 = Y * Y */ |
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99 if ((err = mp_sqr(R->y, t2)) != CRYPT_OK) { goto done; } |
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100 if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; } |
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101 /* T2 = T2/2 */ |
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102 if (mp_isodd(t2)) { |
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103 if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK) { goto done; } |
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104 } |
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105 if ((err = mp_div_2(t2, t2)) != CRYPT_OK) { goto done; } |
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106 /* Y = Y * X */ |
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107 if ((err = mp_mul(R->y, R->x, R->y)) != CRYPT_OK) { goto done; } |
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108 if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK) { goto done; } |
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109 |
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110 /* X = T1 * T1 */ |
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111 if ((err = mp_sqr(t1, R->x)) != CRYPT_OK) { goto done; } |
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112 if ((err = mp_montgomery_reduce(R->x, modulus, mp)) != CRYPT_OK) { goto done; } |
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113 /* X = X - Y */ |
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114 if ((err = mp_sub(R->x, R->y, R->x)) != CRYPT_OK) { goto done; } |
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115 if (mp_cmp_d(R->x, 0) == LTC_MP_LT) { |
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116 if ((err = mp_add(R->x, modulus, R->x)) != CRYPT_OK) { goto done; } |
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117 } |
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118 /* X = X - Y */ |
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119 if ((err = mp_sub(R->x, R->y, R->x)) != CRYPT_OK) { goto done; } |
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120 if (mp_cmp_d(R->x, 0) == LTC_MP_LT) { |
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121 if ((err = mp_add(R->x, modulus, R->x)) != CRYPT_OK) { goto done; } |
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122 } |
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123 |
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124 /* Y = Y - X */ |
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125 if ((err = mp_sub(R->y, R->x, R->y)) != CRYPT_OK) { goto done; } |
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126 if (mp_cmp_d(R->y, 0) == LTC_MP_LT) { |
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127 if ((err = mp_add(R->y, modulus, R->y)) != CRYPT_OK) { goto done; } |
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128 } |
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129 /* Y = Y * T1 */ |
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130 if ((err = mp_mul(R->y, t1, R->y)) != CRYPT_OK) { goto done; } |
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131 if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK) { goto done; } |
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132 /* Y = Y - T2 */ |
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133 if ((err = mp_sub(R->y, t2, R->y)) != CRYPT_OK) { goto done; } |
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134 if (mp_cmp_d(R->y, 0) == LTC_MP_LT) { |
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135 if ((err = mp_add(R->y, modulus, R->y)) != CRYPT_OK) { goto done; } |
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136 } |
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137 |
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138 err = CRYPT_OK; |
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139 done: |
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140 mp_clear_multi(t1, t2, NULL); |
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141 return err; |
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142 } |
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143 #endif |
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144 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_projective_dbl_point.c,v $ */ |
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145 /* $Revision: 1.8 $ */ |
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146 /* $Date: 2006/12/04 05:07:59 $ */ |
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147 |
