view libtommath/bn_mp_dr_is_modulus.c @ 1692:1051e4eea25a

Update LibTomMath to 1.2.0 (#84) * update C files * update other files * update headers * update makefiles * remove mp_set/get_double() * use ltm 1.2.0 API * update ltm_desc * use bundled tommath if system-tommath is too old * XMALLOC etc. were changed to MP_MALLOC etc.
author Steffen Jaeckel <s@jaeckel.eu>
date Tue, 26 May 2020 17:36:47 +0200
parents f52919ffd3b1
children
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#include "tommath_private.h"
#ifdef BN_MP_DR_IS_MODULUS_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* determines if a number is a valid DR modulus */
mp_bool mp_dr_is_modulus(const mp_int *a)
{
   int ix;

   /* must be at least two digits */
   if (a->used < 2) {
      return MP_NO;
   }

   /* must be of the form b**k - a [a <= b] so all
    * but the first digit must be equal to -1 (mod b).
    */
   for (ix = 1; ix < a->used; ix++) {
      if (a->dp[ix] != MP_MASK) {
         return MP_NO;
      }
   }
   return MP_YES;
}

#endif