Mercurial > dropbear
comparison bn_mp_exteuclid.c @ 2:86e0b50a9b58 libtommath-orig ltm-0.30-orig
ltm 0.30 orig import
| author | Matt Johnston <matt@ucc.asn.au> |
|---|---|
| date | Mon, 31 May 2004 18:25:22 +0000 |
| parents | |
| children | d29b64170cf0 |
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| -1:000000000000 | 2:86e0b50a9b58 |
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| 1 /* LibTomMath, multiple-precision integer library -- Tom St Denis | |
| 2 * | |
| 3 * LibTomMath is a library that provides multiple-precision | |
| 4 * integer arithmetic as well as number theoretic functionality. | |
| 5 * | |
| 6 * The library was designed directly after the MPI library by | |
| 7 * Michael Fromberger but has been written from scratch with | |
| 8 * additional optimizations in place. | |
| 9 * | |
| 10 * The library is free for all purposes without any express | |
| 11 * guarantee it works. | |
| 12 * | |
| 13 * Tom St Denis, [email protected], http://math.libtomcrypt.org | |
| 14 */ | |
| 15 #include <tommath.h> | |
| 16 | |
| 17 /* Extended euclidean algorithm of (a, b) produces | |
| 18 a*u1 + b*u2 = u3 | |
| 19 */ | |
| 20 int mp_exteuclid(mp_int *a, mp_int *b, mp_int *U1, mp_int *U2, mp_int *U3) | |
| 21 { | |
| 22 mp_int u1,u2,u3,v1,v2,v3,t1,t2,t3,q,tmp; | |
| 23 int err; | |
| 24 | |
| 25 if ((err = mp_init_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL)) != MP_OKAY) { | |
| 26 return err; | |
| 27 } | |
| 28 | |
| 29 /* initialize, (u1,u2,u3) = (1,0,a) */ | |
| 30 mp_set(&u1, 1); | |
| 31 if ((err = mp_copy(a, &u3)) != MP_OKAY) { goto _ERR; } | |
| 32 | |
| 33 /* initialize, (v1,v2,v3) = (0,1,b) */ | |
| 34 mp_set(&v2, 1); | |
| 35 if ((err = mp_copy(b, &v3)) != MP_OKAY) { goto _ERR; } | |
| 36 | |
| 37 /* loop while v3 != 0 */ | |
| 38 while (mp_iszero(&v3) == MP_NO) { | |
| 39 /* q = u3/v3 */ | |
| 40 if ((err = mp_div(&u3, &v3, &q, NULL)) != MP_OKAY) { goto _ERR; } | |
| 41 | |
| 42 /* (t1,t2,t3) = (u1,u2,u3) - (v1,v2,v3)q */ | |
| 43 if ((err = mp_mul(&v1, &q, &tmp)) != MP_OKAY) { goto _ERR; } | |
| 44 if ((err = mp_sub(&u1, &tmp, &t1)) != MP_OKAY) { goto _ERR; } | |
| 45 if ((err = mp_mul(&v2, &q, &tmp)) != MP_OKAY) { goto _ERR; } | |
| 46 if ((err = mp_sub(&u2, &tmp, &t2)) != MP_OKAY) { goto _ERR; } | |
| 47 if ((err = mp_mul(&v3, &q, &tmp)) != MP_OKAY) { goto _ERR; } | |
| 48 if ((err = mp_sub(&u3, &tmp, &t3)) != MP_OKAY) { goto _ERR; } | |
| 49 | |
| 50 /* (u1,u2,u3) = (v1,v2,v3) */ | |
| 51 if ((err = mp_copy(&v1, &u1)) != MP_OKAY) { goto _ERR; } | |
| 52 if ((err = mp_copy(&v2, &u2)) != MP_OKAY) { goto _ERR; } | |
| 53 if ((err = mp_copy(&v3, &u3)) != MP_OKAY) { goto _ERR; } | |
| 54 | |
| 55 /* (v1,v2,v3) = (t1,t2,t3) */ | |
| 56 if ((err = mp_copy(&t1, &v1)) != MP_OKAY) { goto _ERR; } | |
| 57 if ((err = mp_copy(&t2, &v2)) != MP_OKAY) { goto _ERR; } | |
| 58 if ((err = mp_copy(&t3, &v3)) != MP_OKAY) { goto _ERR; } | |
| 59 } | |
| 60 | |
| 61 /* copy result out */ | |
| 62 if (U1 != NULL) { mp_exch(U1, &u1); } | |
| 63 if (U2 != NULL) { mp_exch(U2, &u2); } | |
| 64 if (U3 != NULL) { mp_exch(U3, &u3); } | |
| 65 | |
| 66 err = MP_OKAY; | |
| 67 _ERR: mp_clear_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL); | |
| 68 return err; | |
| 69 } |