blob: c4ebab4b5f1d6ae168e700637b88fb8f5e382e4b [file] [log] [blame]
 #include #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@iahu.ca, http://math.libtomcrypt.org */ /* 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