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comparison libtommath/bn_mp_dr_is_modulus.c @ 293:9d110777f345 contrib-blacklist

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propagate from branch 'au.asn.ucc.matt.dropbear' (head 7ad1775ed65e75dbece27fe6b65bf1a234db386a) to branch 'au.asn.ucc.matt.dropbear.contrib.blacklist' (head 1d86a4f0a401cc68c2670d821a2f6366c37af143)
author Matt Johnston <matt@ucc.asn.au>
date Fri, 10 Mar 2006 06:31:29 +0000
parents eed26cff980b
children 5ff8218bcee9
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247:c07de41b53d7 293:9d110777f345
1 #include <tommath.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, [email protected], http://math.libtomcrypt.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