Mercurial > dropbear

comparison bn_fast_mp_montgomery_reduce.c @ 142:d29b64170cf0 libtommath-orig

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
import of libtommath 0.32
author Matt Johnston <matt@ucc.asn.au>
date Sun, 19 Dec 2004 11:33:56 +0000
parents 86e0b50a9b58
children d8254fc979e9
comparison
equal deleted inserted replaced
19:e1037a1e12e7 142:d29b64170cf0
1 #include <tommath.h>
2 #ifdef BN_FAST_MP_MONTGOMERY_REDUCE_C
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
2 * 4 *
3 * LibTomMath is a library that provides multiple-precision 5 * LibTomMath is a library that provides multiple-precision
4 * integer arithmetic as well as number theoretic functionality. 6 * integer arithmetic as well as number theoretic functionality.
5 * 7 *
10 * The library is free for all purposes without any express 12 * The library is free for all purposes without any express
11 * guarantee it works. 13 * guarantee it works.
12 * 14 *
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org 15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
14 */ 16 */
15 #include <tommath.h>
16 17
17 /* computes xR**-1 == x (mod N) via Montgomery Reduction 18 /* computes xR**-1 == x (mod N) via Montgomery Reduction
18 * 19 *
19 * This is an optimized implementation of mp_montgomery_reduce 20 * This is an optimized implementation of montgomery_reduce
20 * which uses the comba method to quickly calculate the columns of the 21 * which uses the comba method to quickly calculate the columns of the
21 * reduction. 22 * reduction.
22 * 23 *
23 * Based on Algorithm 14.32 on pp.601 of HAC. 24 * Based on Algorithm 14.32 on pp.601 of HAC.
24 */ 25 */
163 if (mp_cmp_mag (x, n) != MP_LT) { 164 if (mp_cmp_mag (x, n) != MP_LT) {
164 return s_mp_sub (x, n, x); 165 return s_mp_sub (x, n, x);
165 } 166 }
166 return MP_OKAY; 167 return MP_OKAY;
167 } 168 }
169 #endif