tommath/bn_mp_dr_is_modulus.c
Steffen Jaeckel 4e3f1344a5 provide tommath_private.h
tommath.h contains declarations for the public part of the library.
tommath_private.h contains the functions which are private to ltm and
should not be exposed to the public.
2015-11-12 01:49:07 +01:00

44 lines
1.0 KiB
C

#include <tommath_private.h>
#ifdef BN_MP_DR_IS_MODULUS_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tstdenis82@gmail.com, http://libtom.org
*/
/* determines if a number is a valid DR modulus */
int mp_dr_is_modulus(mp_int *a)
{
int ix;
/* must be at least two digits */
if (a->used < 2) {
return 0;
}
/* 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 0;
}
}
return 1;
}
#endif
/* $Source$ */
/* $Revision$ */
/* $Date$ */