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comparison libtommath/bn_mp_expt_d.c @ 1436:60fc6476e044

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Update to libtommath v1.0
author Matt Johnston <matt@ucc.asn.au>
date Sat, 24 Jun 2017 22:37:14 +0800
parents 5ff8218bcee9
children 8bba51a55704
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1435:f849a5ca2efc 1436:60fc6476e044
1 #include <tommath.h> 1 #include <tommath_private.h>
2 #ifdef BN_MP_EXPT_D_C 2 #ifdef BN_MP_EXPT_D_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 * 4 *
5 * LibTomMath is a library that provides multiple-precision 5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality. 6 * integer arithmetic as well as number theoretic functionality.
10 * additional optimizations in place. 10 * additional optimizations in place.
11 * 11 *
12 * The library is free for all purposes without any express 12 * The library is free for all purposes without any express
13 * guarantee it works. 13 * guarantee it works.
14 * 14 *
15 * Tom St Denis, [email protected], http://math.libtomcrypt.com 15 * Tom St Denis, [email protected], http://libtom.org
16 */ 16 */
17 17
18 /* calculate c = a**b using a square-multiply algorithm */ 18 /* wrapper function for mp_expt_d_ex() */
19 int mp_expt_d (mp_int * a, mp_digit b, mp_int * c) 19 int mp_expt_d (mp_int * a, mp_digit b, mp_int * c)
20 { 20 {
21 int res, x; 21 return mp_expt_d_ex(a, b, c, 0);
22 mp_int g; 22 }
23 23
24 if ((res = mp_init_copy (&g, a)) != MP_OKAY) {
25 return res;
26 }
27
28 /* set initial result */
29 mp_set (c, 1);
30
31 for (x = 0; x < (int) DIGIT_BIT; x++) {
32 /* square */
33 if ((res = mp_sqr (c, c)) != MP_OKAY) {
34 mp_clear (&g);
35 return res;
36 }
37
38 /* if the bit is set multiply */
39 if ((b & (mp_digit) (((mp_digit)1) << (DIGIT_BIT - 1))) != 0) {
40 if ((res = mp_mul (c, &g, c)) != MP_OKAY) {
41 mp_clear (&g);
42 return res;
43 }
44 }
45
46 /* shift to next bit */
47 b <<= 1;
48 }
49
50 mp_clear (&g);
51 return MP_OKAY;
52 }
53 #endif 24 #endif
54 25
55 /* $Source: /cvs/libtom/libtommath/bn_mp_expt_d.c,v $ */ 26 /* $Source$ */
56 /* $Revision: 1.3 $ */ 27 /* $Revision$ */
57 /* $Date: 2006/03/31 14:18:44 $ */ 28 /* $Date$ */