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#include "tommath_private.h"
#ifdef 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 */
bool mp_dr_is_modulus(const mp_int *a)
{
int ix;
/* must be at least two digits */
if (a->used < 2) {
return false;
}
/* 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 false;
}
}
return true;
}
#endif
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