# publiclibtom/libtommath

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 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 `/* LibTomMath, multiple-precision integer library -- Tom St Denis * * LibTomMath is library that provides for multiple-precision * integer arithmetic as well as number theoretic functionality. * * The library is 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, tomstdenis@iahu.ca, http://math.libtomcrypt.org */#include /* performs one Fermat test. * * If "a" were prime then b^a == b (mod a) since the order of * the multiplicative sub-group would be phi(a) = a-1. That means * it would be the same as b^(a mod (a-1)) == b^1 == b (mod a). * * Sets result to 1 if the congruence holds, or zero otherwise. */intmp_prime_fermat (mp_int * a, mp_int * b, int *result){  mp_int t;  int err;  /* default to fail */  *result = 0;  /* init t */  if ((err = mp_init (&t)) != MP_OKAY) {    return err;  }  /* compute t = b^a mod a */  if ((err = mp_exptmod (b, a, a, &t)) != MP_OKAY) {    goto __T;  }  /* is it equal to b? */  if (mp_cmp (&t, b) == MP_EQ) {    *result = 1;  }  err = MP_OKAY;__T:mp_clear (&t);  return err;}`
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