Mercurial > dropbear
annotate bn_mp_exteuclid.c @ 190:d8254fc979e9 libtommath-orig LTM_0.35
Initial import of libtommath 0.35
| author | Matt Johnston <matt@ucc.asn.au> |
|---|---|
| date | Fri, 06 May 2005 08:59:30 +0000 |
| parents | d29b64170cf0 |
| children |
| rev | line source |
|---|---|
| 142 | 1 #include <tommath.h> |
| 2 #ifdef BN_MP_EXTEUCLID_C | |
| 2 | 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
| 4 * | |
| 5 * LibTomMath is a library that provides multiple-precision | |
| 6 * integer arithmetic as well as number theoretic functionality. | |
| 7 * | |
| 8 * The library was designed directly after the MPI library by | |
| 9 * Michael Fromberger but has been written from scratch with | |
| 10 * additional optimizations in place. | |
| 11 * | |
| 12 * The library is free for all purposes without any express | |
| 13 * guarantee it works. | |
| 14 * | |
| 15 * Tom St Denis, [email protected], http://math.libtomcrypt.org | |
| 16 */ | |
| 17 | |
| 18 /* Extended euclidean algorithm of (a, b) produces | |
| 19 a*u1 + b*u2 = u3 | |
| 20 */ | |
| 21 int mp_exteuclid(mp_int *a, mp_int *b, mp_int *U1, mp_int *U2, mp_int *U3) | |
| 22 { | |
| 23 mp_int u1,u2,u3,v1,v2,v3,t1,t2,t3,q,tmp; | |
| 24 int err; | |
| 25 | |
| 26 if ((err = mp_init_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL)) != MP_OKAY) { | |
| 27 return err; | |
| 28 } | |
| 29 | |
| 30 /* initialize, (u1,u2,u3) = (1,0,a) */ | |
| 31 mp_set(&u1, 1); | |
| 32 if ((err = mp_copy(a, &u3)) != MP_OKAY) { goto _ERR; } | |
| 33 | |
| 34 /* initialize, (v1,v2,v3) = (0,1,b) */ | |
| 35 mp_set(&v2, 1); | |
| 36 if ((err = mp_copy(b, &v3)) != MP_OKAY) { goto _ERR; } | |
| 37 | |
| 38 /* loop while v3 != 0 */ | |
| 39 while (mp_iszero(&v3) == MP_NO) { | |
| 40 /* q = u3/v3 */ | |
| 41 if ((err = mp_div(&u3, &v3, &q, NULL)) != MP_OKAY) { goto _ERR; } | |
| 42 | |
| 43 /* (t1,t2,t3) = (u1,u2,u3) - (v1,v2,v3)q */ | |
| 44 if ((err = mp_mul(&v1, &q, &tmp)) != MP_OKAY) { goto _ERR; } | |
| 45 if ((err = mp_sub(&u1, &tmp, &t1)) != MP_OKAY) { goto _ERR; } | |
| 46 if ((err = mp_mul(&v2, &q, &tmp)) != MP_OKAY) { goto _ERR; } | |
| 47 if ((err = mp_sub(&u2, &tmp, &t2)) != MP_OKAY) { goto _ERR; } | |
| 48 if ((err = mp_mul(&v3, &q, &tmp)) != MP_OKAY) { goto _ERR; } | |
| 49 if ((err = mp_sub(&u3, &tmp, &t3)) != MP_OKAY) { goto _ERR; } | |
| 50 | |
| 51 /* (u1,u2,u3) = (v1,v2,v3) */ | |
| 52 if ((err = mp_copy(&v1, &u1)) != MP_OKAY) { goto _ERR; } | |
| 53 if ((err = mp_copy(&v2, &u2)) != MP_OKAY) { goto _ERR; } | |
| 54 if ((err = mp_copy(&v3, &u3)) != MP_OKAY) { goto _ERR; } | |
| 55 | |
| 56 /* (v1,v2,v3) = (t1,t2,t3) */ | |
| 57 if ((err = mp_copy(&t1, &v1)) != MP_OKAY) { goto _ERR; } | |
| 58 if ((err = mp_copy(&t2, &v2)) != MP_OKAY) { goto _ERR; } | |
| 59 if ((err = mp_copy(&t3, &v3)) != MP_OKAY) { goto _ERR; } | |
| 60 } | |
| 61 | |
|
190
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
62 /* make sure U3 >= 0 */ |
|
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
63 if (u3.sign == MP_NEG) { |
|
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
64 mp_neg(&u1, &u1); |
|
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
65 mp_neg(&u2, &u2); |
|
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
66 mp_neg(&u3, &u3); |
|
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
67 } |
|
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
68 |
| 2 | 69 /* copy result out */ |
| 70 if (U1 != NULL) { mp_exch(U1, &u1); } | |
| 71 if (U2 != NULL) { mp_exch(U2, &u2); } | |
| 72 if (U3 != NULL) { mp_exch(U3, &u3); } | |
| 73 | |
| 74 err = MP_OKAY; | |
| 75 _ERR: mp_clear_multi(&u1, &u2, &u3, &v1, &v2, &v3, &t1, &t2, &t3, &q, &tmp, NULL); | |
| 76 return err; | |
| 77 } | |
| 142 | 78 #endif |