view libtommath/bn_mp_exteuclid.c @ 1655:f52919ffd3b1

update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79) * make key-generation compliant to FIPS 186.4 * fix includes in tommath_class.h * update fuzzcorpus instead of error-out * fixup fuzzing make-targets * update Makefile.in * apply necessary patches to ltm sources * clean-up not required ltm files * update to vanilla ltm 1.1.0 this already only contains the required files * remove set/get double
author Steffen Jaeckel <s_jaeckel@gmx.de>
date Mon, 16 Sep 2019 15:50:38 +0200
parents 8bba51a55704
children 1051e4eea25a
line wrap: on
line source
#include "tommath_private.h"
#ifdef BN_MP_EXTEUCLID_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.
 *
 * SPDX-License-Identifier: Unlicense
 */

/* Extended euclidean algorithm of (a, b) produces
   a*u1 + b*u2 = u3
 */
int mp_exteuclid(const mp_int *a, const mp_int *b, mp_int *U1, mp_int *U2, mp_int *U3)
{
   mp_int u1, u2, u3, v1, v2, v3, t1, t2, t3, q, tmp;
   int err;

   if ((err = mp_init_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL)) != MP_OKAY) {
      return err;
   }

   /* initialize, (u1,u2,u3) = (1,0,a) */
   mp_set(&u1, 1uL);
   if ((err = mp_copy(a, &u3)) != MP_OKAY) {
      goto LBL_ERR;
   }

   /* initialize, (v1,v2,v3) = (0,1,b) */
   mp_set(&v2, 1uL);
   if ((err = mp_copy(b, &v3)) != MP_OKAY) {
      goto LBL_ERR;
   }

   /* loop while v3 != 0 */
   while (mp_iszero(&v3) == MP_NO) {
      /* q = u3/v3 */
      if ((err = mp_div(&u3, &v3, &q, NULL)) != MP_OKAY) {
         goto LBL_ERR;
      }

      /* (t1,t2,t3) = (u1,u2,u3) - (v1,v2,v3)q */
      if ((err = mp_mul(&v1, &q, &tmp)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_sub(&u1, &tmp, &t1)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_mul(&v2, &q, &tmp)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_sub(&u2, &tmp, &t2)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_mul(&v3, &q, &tmp)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_sub(&u3, &tmp, &t3)) != MP_OKAY) {
         goto LBL_ERR;
      }

      /* (u1,u2,u3) = (v1,v2,v3) */
      if ((err = mp_copy(&v1, &u1)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_copy(&v2, &u2)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_copy(&v3, &u3)) != MP_OKAY) {
         goto LBL_ERR;
      }

      /* (v1,v2,v3) = (t1,t2,t3) */
      if ((err = mp_copy(&t1, &v1)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_copy(&t2, &v2)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_copy(&t3, &v3)) != MP_OKAY) {
         goto LBL_ERR;
      }
   }

   /* make sure U3 >= 0 */
   if (u3.sign == MP_NEG) {
      if ((err = mp_neg(&u1, &u1)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_neg(&u2, &u2)) != MP_OKAY) {
         goto LBL_ERR;
      }
      if ((err = mp_neg(&u3, &u3)) != MP_OKAY) {
         goto LBL_ERR;
      }
   }

   /* copy result out */
   if (U1 != NULL) {
      mp_exch(U1, &u1);
   }
   if (U2 != NULL) {
      mp_exch(U2, &u2);
   }
   if (U3 != NULL) {
      mp_exch(U3, &u3);
   }

   err = MP_OKAY;
LBL_ERR:
   mp_clear_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL);
   return err;
}
#endif

/* ref:         HEAD -> master, tag: v1.1.0 */
/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
/* commit time: 2019-01-28 20:32:32 +0100 */