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comparison 3rdparty/libtommath/bn_mp_dr_is_modulus.c @ 0:2cf249471370

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author Takahiro SHIMIZU <anatofuz@cr.ie.u-ryukyu.ac.jp>
date Tue, 08 May 2018 16:09:12 +0900
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1 #include <tommath_private.h>
2 #ifdef BN_MP_DR_IS_MODULUS_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, tstdenis82@gmail.com, http://libtom.org
16 */
17
18 /* determines if a number is a valid DR modulus */
19 int mp_dr_is_modulus(mp_int *a)
20 {
21 int ix;
22
23 /* must be at least two digits */
24 if (a->used < 2) {
25 return 0;
26 }
27
28 /* must be of the form b**k - a [a <= b] so all
29 * but the first digit must be equal to -1 (mod b).
30 */
31 for (ix = 1; ix < a->used; ix++) {
32 if (a->dp[ix] != MP_MASK) {
33 return 0;
34 }
35 }
36 return 1;
37 }
38
39 #endif
40
41 /* $Source$ */
42 /* $Revision$ */
43 /* $Date$ */