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annotate libtommath/bn_s_mp_invmod_fast.c @ 1930:299f4f19ba19

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Add /usr/sbin and /sbin to default root PATH When dropbear is used in a very restricted environment (such as in a initrd), the default user shell is often also very restricted and doesn't take care of setting the PATH so the user ends up with the PATH set by dropbear. Unfortunately, dropbear always sets "/usr/bin:/bin" as default PATH even for the root user which should have /usr/sbin and /sbin too. For a concrete instance of this problem, see the "Remote Unlocking" section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/ It speaks of a bug in the initramfs script because it's written "blkid" instead of "/sbin/blkid"... this is just because the scripts from the initramfs do not expect to have a PATH without the sbin directories and because dropbear is not setting the PATH appropriately for the root user. I'm thus suggesting to use the attached patch to fix this misbehaviour (I did not test it, but it's easy enough). It might seem anecdotic but multiple Kali users have been bitten by this. From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author Raphael Hertzog <hertzog@debian.org>
date Mon, 09 Jul 2018 16:27:53 +0200
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>
parents:
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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_INVMOD_FAST_C
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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diff changeset
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 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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5
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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6 /* computes the modular inverse via binary extended euclidean algorithm,
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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7 * that is c = 1/a mod b
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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8 *
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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9 * Based on slow invmod except this is optimized for the case where b is
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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10 * odd as per HAC Note 14.64 on pp. 610
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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11 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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12 mp_err s_mp_invmod_fast(const mp_int *a, const mp_int *b, mp_int *c)
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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13 {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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14 mp_int x, y, u, v, B, D;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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15 mp_sign neg;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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16 mp_err err;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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17
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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18 /* 2. [modified] b must be odd */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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19 if (MP_IS_EVEN(b)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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20 return MP_VAL;
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21 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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22
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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23 /* init all our temps */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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24 if ((err = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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25 return err;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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26 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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27
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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28 /* x == modulus, y == value to invert */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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29 if ((err = mp_copy(b, &x)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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30
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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31 /* we need y = |a| */
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32 if ((err = mp_mod(a, b, &y)) != MP_OKAY) goto LBL_ERR;
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33
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34 /* if one of x,y is zero return an error! */
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35 if (MP_IS_ZERO(&x) || MP_IS_ZERO(&y)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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36 err = MP_VAL;
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37 goto LBL_ERR;
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38 }
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39
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40 /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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41 if ((err = mp_copy(&x, &u)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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42 if ((err = mp_copy(&y, &v)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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43 mp_set(&D, 1uL);
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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44
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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45 top:
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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46 /* 4. while u is even do */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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47 while (MP_IS_EVEN(&u)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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48 /* 4.1 u = u/2 */
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49 if ((err = mp_div_2(&u, &u)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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50
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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51 /* 4.2 if B is odd then */
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Steffen Jaeckel <s@jaeckel.eu>
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52 if (MP_IS_ODD(&B)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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53 if ((err = mp_sub(&B, &x, &B)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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54 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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55 /* B = B/2 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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56 if ((err = mp_div_2(&B, &B)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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57 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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58
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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59 /* 5. while v is even do */
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60 while (MP_IS_EVEN(&v)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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61 /* 5.1 v = v/2 */
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Steffen Jaeckel <s@jaeckel.eu>
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62 if ((err = mp_div_2(&v, &v)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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63
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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64 /* 5.2 if D is odd then */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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65 if (MP_IS_ODD(&D)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
66 /* D = (D-x)/2 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
67 if ((err = mp_sub(&D, &x, &D)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
68 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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69 /* D = D/2 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
70 if ((err = mp_div_2(&D, &D)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
71 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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72
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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73 /* 6. if u >= v then */
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Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
74 if (mp_cmp(&u, &v) != MP_LT) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
75 /* u = u - v, B = B - D */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
76 if ((err = mp_sub(&u, &v, &u)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
77
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
78 if ((err = mp_sub(&B, &D, &B)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
79 } else {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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80 /* v - v - u, D = D - B */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
81 if ((err = mp_sub(&v, &u, &v)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
82
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
83 if ((err = mp_sub(&D, &B, &D)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
84 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
85
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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86 /* if not zero goto step 4 */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
87 if (!MP_IS_ZERO(&u)) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
88 goto top;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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89 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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90
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91 /* now a = C, b = D, gcd == g*v */
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diff changeset
92
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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93 /* if v != 1 then there is no inverse */
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Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
94 if (mp_cmp_d(&v, 1uL) != MP_EQ) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
95 err = MP_VAL;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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96 goto LBL_ERR;
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Steffen Jaeckel <s@jaeckel.eu>
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97 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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diff changeset
98
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99 /* b is now the inverse */
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
100 neg = a->sign;
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Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
101 while (D.sign == MP_NEG) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
102 if ((err = mp_add(&D, b, &D)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
103 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
104
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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105 /* too big */
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Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
106 while (mp_cmp_mag(&D, b) != MP_LT) {
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
107 if ((err = mp_sub(&D, b, &D)) != MP_OKAY) goto LBL_ERR;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
parents:
diff changeset
108 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
109
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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110 mp_exch(&D, c);
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Steffen Jaeckel <s@jaeckel.eu>
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111 c->sign = neg;
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Steffen Jaeckel <s@jaeckel.eu>
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112 err = MP_OKAY;
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Steffen Jaeckel <s@jaeckel.eu>
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diff changeset
113
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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114 LBL_ERR:
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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115 mp_clear_multi(&x, &y, &u, &v, &B, &D, NULL);
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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116 return err;
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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117 }
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
Steffen Jaeckel <s@jaeckel.eu>
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118 #endif