Mercurial > dropbear

annotate libtommath/bn_s_mp_karatsuba_sqr.c @ 1902:4a6725ac957c

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Revert "Don't include sk keys at all in KEX list" This reverts git commit f972813ecdc7bb981d25b5a63638bd158f1c8e72. The sk algorithms need to remain in the sigalgs list so that they are included in the server-sig-algs ext-info message sent by the server. RFC8308 for server-sig-algs requires that all algorithms are listed (though OpenSSH client 8.4p1 tested doesn't require that)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 24 Mar 2022 13:42:08 +0800
parents 1051e4eea25a
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1692
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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1 #include "tommath_private.h"
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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2 #ifdef BN_S_MP_KARATSUBA_SQR_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
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4 /* SPDX-License-Identifier: Unlicense */
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5
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6 /* Karatsuba squaring, computes b = a*a using three
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7 * half size squarings
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8 *
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9 * See comments of karatsuba_mul for details. It
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10 * is essentially the same algorithm but merely
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11 * tuned to perform recursive squarings.
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12 */
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13 mp_err s_mp_karatsuba_sqr(const mp_int *a, mp_int *b)
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14 {
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15 mp_int x0, x1, t1, t2, x0x0, x1x1;
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16 int B;
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17 mp_err err = MP_MEM;
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18
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19 /* min # of digits */
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20 B = a->used;
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21
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22 /* now divide in two */
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23 B = B >> 1;
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24
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25 /* init copy all the temps */
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26 if (mp_init_size(&x0, B) != MP_OKAY)
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27 goto LBL_ERR;
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28 if (mp_init_size(&x1, a->used - B) != MP_OKAY)
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29 goto X0;
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30
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31 /* init temps */
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32 if (mp_init_size(&t1, a->used * 2) != MP_OKAY)
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33 goto X1;
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34 if (mp_init_size(&t2, a->used * 2) != MP_OKAY)
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35 goto T1;
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36 if (mp_init_size(&x0x0, B * 2) != MP_OKAY)
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37 goto T2;
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38 if (mp_init_size(&x1x1, (a->used - B) * 2) != MP_OKAY)
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39 goto X0X0;
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40
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41 {
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42 int x;
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43 mp_digit *dst, *src;
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44
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45 src = a->dp;
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46
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47 /* now shift the digits */
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48 dst = x0.dp;
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49 for (x = 0; x < B; x++) {
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50 *dst++ = *src++;
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51 }
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52
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53 dst = x1.dp;
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54 for (x = B; x < a->used; x++) {
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55 *dst++ = *src++;
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56 }
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57 }
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58
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59 x0.used = B;
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60 x1.used = a->used - B;
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61
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62 mp_clamp(&x0);
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63
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64 /* now calc the products x0*x0 and x1*x1 */
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65 if (mp_sqr(&x0, &x0x0) != MP_OKAY)
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66 goto X1X1; /* x0x0 = x0*x0 */
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67 if (mp_sqr(&x1, &x1x1) != MP_OKAY)
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68 goto X1X1; /* x1x1 = x1*x1 */
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69
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70 /* now calc (x1+x0)**2 */
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71 if (s_mp_add(&x1, &x0, &t1) != MP_OKAY)
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72 goto X1X1; /* t1 = x1 - x0 */
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73 if (mp_sqr(&t1, &t1) != MP_OKAY)
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74 goto X1X1; /* t1 = (x1 - x0) * (x1 - x0) */
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75
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76 /* add x0y0 */
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77 if (s_mp_add(&x0x0, &x1x1, &t2) != MP_OKAY)
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78 goto X1X1; /* t2 = x0x0 + x1x1 */
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79 if (s_mp_sub(&t1, &t2, &t1) != MP_OKAY)
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80 goto X1X1; /* t1 = (x1+x0)**2 - (x0x0 + x1x1) */
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81
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82 /* shift by B */
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83 if (mp_lshd(&t1, B) != MP_OKAY)
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84 goto X1X1; /* t1 = (x0x0 + x1x1 - (x1-x0)*(x1-x0))<<B */
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85 if (mp_lshd(&x1x1, B * 2) != MP_OKAY)
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86 goto X1X1; /* x1x1 = x1x1 << 2*B */
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87
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88 if (mp_add(&x0x0, &t1, &t1) != MP_OKAY)
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89 goto X1X1; /* t1 = x0x0 + t1 */
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90 if (mp_add(&t1, &x1x1, b) != MP_OKAY)
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91 goto X1X1; /* t1 = x0x0 + t1 + x1x1 */
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92
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93 err = MP_OKAY;
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94
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95 X1X1:
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96 mp_clear(&x1x1);
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97 X0X0:
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98 mp_clear(&x0x0);
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99 T2:
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100 mp_clear(&t2);
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101 T1:
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102 mp_clear(&t1);
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103 X1:
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104 mp_clear(&x1);
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105 X0:
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106 mp_clear(&x0);
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107 LBL_ERR:
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108 return err;
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109 }
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110 #endif