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, tomstdenis@gmail.com, http://libtom.org
16 */
17
18/* determines if a number is a valid DR modulus */
19int 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/* $Date$ */
44