mirror of
http://galexander.org/git/simplesshd.git
synced 2024-11-18 05:18:47 +00:00
83 lines
3.2 KiB
C
83 lines
3.2 KiB
C
#include <tommath.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.
|
|
*
|
|
* The library is free for all purposes without any express
|
|
* guarantee it works.
|
|
*
|
|
* Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
|
|
*/
|
|
|
|
/* Extended euclidean algorithm of (a, b) produces
|
|
a*u1 + b*u2 = u3
|
|
*/
|
|
int mp_exteuclid(mp_int *a, 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, 1);
|
|
if ((err = mp_copy(a, &u3)) != MP_OKAY) { goto _ERR; }
|
|
|
|
/* initialize, (v1,v2,v3) = (0,1,b) */
|
|
mp_set(&v2, 1);
|
|
if ((err = mp_copy(b, &v3)) != MP_OKAY) { goto _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 _ERR; }
|
|
|
|
/* (t1,t2,t3) = (u1,u2,u3) - (v1,v2,v3)q */
|
|
if ((err = mp_mul(&v1, &q, &tmp)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_sub(&u1, &tmp, &t1)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_mul(&v2, &q, &tmp)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_sub(&u2, &tmp, &t2)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_mul(&v3, &q, &tmp)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_sub(&u3, &tmp, &t3)) != MP_OKAY) { goto _ERR; }
|
|
|
|
/* (u1,u2,u3) = (v1,v2,v3) */
|
|
if ((err = mp_copy(&v1, &u1)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_copy(&v2, &u2)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_copy(&v3, &u3)) != MP_OKAY) { goto _ERR; }
|
|
|
|
/* (v1,v2,v3) = (t1,t2,t3) */
|
|
if ((err = mp_copy(&t1, &v1)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_copy(&t2, &v2)) != MP_OKAY) { goto _ERR; }
|
|
if ((err = mp_copy(&t3, &v3)) != MP_OKAY) { goto _ERR; }
|
|
}
|
|
|
|
/* make sure U3 >= 0 */
|
|
if (u3.sign == MP_NEG) {
|
|
mp_neg(&u1, &u1);
|
|
mp_neg(&u2, &u2);
|
|
mp_neg(&u3, &u3);
|
|
}
|
|
|
|
/* 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;
|
|
_ERR: mp_clear_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL);
|
|
return err;
|
|
}
|
|
#endif
|
|
|
|
/* $Source: /cvs/libtom/libtommath/bn_mp_exteuclid.c,v $ */
|
|
/* $Revision: 1.3 $ */
|
|
/* $Date: 2006/03/31 14:18:44 $ */
|