Mercurial > dropbear

annotate libtommath/bn_s_mp_karatsuba_sqr.c @ 1861:2b3a8026a6ce

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Add re-exec for server This allows ASLR to re-randomize the address space for every connection, preventing some vulnerabilities from being exploitable by repeated probing. Overhead (memory and time) is yet to be confirmed. At present this is only enabled on Linux. Other BSD platforms with fexecve() would probably also work though have not been tested.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Jan 2022 10:14:56 +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)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
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 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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4 /* SPDX-License-Identifier: Unlicense */
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5
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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6 /* Karatsuba squaring, computes b = a*a using three
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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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
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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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;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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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