diff options
Diffstat (limited to 'libtommath/bn_mp_invmod_slow.c')
| -rw-r--r-- | libtommath/bn_mp_invmod_slow.c | 247 |
1 files changed, 124 insertions, 123 deletions
diff --git a/libtommath/bn_mp_invmod_slow.c b/libtommath/bn_mp_invmod_slow.c index ff0d5ae..2bdd2b1 100644 --- a/libtommath/bn_mp_invmod_slow.c +++ b/libtommath/bn_mp_invmod_slow.c @@ -16,157 +16,158 @@ */ /* hac 14.61, pp608 */ -int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c) +int mp_invmod_slow(mp_int *a, mp_int *b, mp_int *c) { - mp_int x, y, u, v, A, B, C, D; - int res; - - /* b cannot be negative */ - if ((b->sign == MP_NEG) || (mp_iszero(b) == MP_YES)) { - return MP_VAL; - } - - /* init temps */ - if ((res = mp_init_multi(&x, &y, &u, &v, - &A, &B, &C, &D, NULL)) != MP_OKAY) { - return res; - } - - /* x = a, y = b */ - if ((res = mp_mod(a, b, &x)) != MP_OKAY) { + mp_int x, y, u, v, A, B, C, D; + int res; + + /* b cannot be negative */ + if ((b->sign == MP_NEG) || (mp_iszero(b) == MP_YES)) { + return MP_VAL; + } + + /* init temps */ + if ((res = mp_init_multi(&x, &y, &u, &v, + &A, &B, &C, &D, NULL)) != MP_OKAY) { + return res; + } + + /* x = a, y = b */ + if ((res = mp_mod(a, b, &x)) != MP_OKAY) { goto LBL_ERR; - } - if ((res = mp_copy (b, &y)) != MP_OKAY) { - goto LBL_ERR; - } - - /* 2. [modified] if x,y are both even then return an error! */ - if ((mp_iseven (&x) == MP_YES) && (mp_iseven (&y) == MP_YES)) { - res = MP_VAL; - goto LBL_ERR; - } - - /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ - if ((res = mp_copy (&x, &u)) != MP_OKAY) { - goto LBL_ERR; - } - if ((res = mp_copy (&y, &v)) != MP_OKAY) { - goto LBL_ERR; - } - mp_set (&A, 1); - mp_set (&D, 1); + } + if ((res = mp_copy(b, &y)) != MP_OKAY) { + goto LBL_ERR; + } -top: - /* 4. while u is even do */ - while (mp_iseven (&u) == MP_YES) { - /* 4.1 u = u/2 */ - if ((res = mp_div_2 (&u, &u)) != MP_OKAY) { + /* 2. [modified] if x,y are both even then return an error! */ + if ((mp_iseven(&x) == MP_YES) && (mp_iseven(&y) == MP_YES)) { + res = MP_VAL; + goto LBL_ERR; + } + + /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ + if ((res = mp_copy(&x, &u)) != MP_OKAY) { + goto LBL_ERR; + } + if ((res = mp_copy(&y, &v)) != MP_OKAY) { goto LBL_ERR; - } - /* 4.2 if A or B is odd then */ - if ((mp_isodd (&A) == MP_YES) || (mp_isodd (&B) == MP_YES)) { - /* A = (A+y)/2, B = (B-x)/2 */ - if ((res = mp_add (&A, &y, &A)) != MP_OKAY) { + } + mp_set(&A, 1); + mp_set(&D, 1); + +top: + /* 4. while u is even do */ + while (mp_iseven(&u) == MP_YES) { + /* 4.1 u = u/2 */ + if ((res = mp_div_2(&u, &u)) != MP_OKAY) { goto LBL_ERR; } - if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) { + /* 4.2 if A or B is odd then */ + if ((mp_isodd(&A) == MP_YES) || (mp_isodd(&B) == MP_YES)) { + /* A = (A+y)/2, B = (B-x)/2 */ + if ((res = mp_add(&A, &y, &A)) != MP_OKAY) { + goto LBL_ERR; + } + if ((res = mp_sub(&B, &x, &B)) != MP_OKAY) { + goto LBL_ERR; + } + } + /* A = A/2, B = B/2 */ + if ((res = mp_div_2(&A, &A)) != MP_OKAY) { goto LBL_ERR; } - } - /* A = A/2, B = B/2 */ - if ((res = mp_div_2 (&A, &A)) != MP_OKAY) { - goto LBL_ERR; - } - if ((res = mp_div_2 (&B, &B)) != MP_OKAY) { - goto LBL_ERR; - } - } + if ((res = mp_div_2(&B, &B)) != MP_OKAY) { + goto LBL_ERR; + } + } - /* 5. while v is even do */ - while (mp_iseven (&v) == MP_YES) { - /* 5.1 v = v/2 */ - if ((res = mp_div_2 (&v, &v)) != MP_OKAY) { - goto LBL_ERR; - } - /* 5.2 if C or D is odd then */ - if ((mp_isodd (&C) == MP_YES) || (mp_isodd (&D) == MP_YES)) { - /* C = (C+y)/2, D = (D-x)/2 */ - if ((res = mp_add (&C, &y, &C)) != MP_OKAY) { + /* 5. while v is even do */ + while (mp_iseven(&v) == MP_YES) { + /* 5.1 v = v/2 */ + if ((res = mp_div_2(&v, &v)) != MP_OKAY) { goto LBL_ERR; } - if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) { + /* 5.2 if C or D is odd then */ + if ((mp_isodd(&C) == MP_YES) || (mp_isodd(&D) == MP_YES)) { + /* C = (C+y)/2, D = (D-x)/2 */ + if ((res = mp_add(&C, &y, &C)) != MP_OKAY) { + goto LBL_ERR; + } + if ((res = mp_sub(&D, &x, &D)) != MP_OKAY) { + goto LBL_ERR; + } + } + /* C = C/2, D = D/2 */ + if ((res = mp_div_2(&C, &C)) != MP_OKAY) { goto LBL_ERR; } - } - /* C = C/2, D = D/2 */ - if ((res = mp_div_2 (&C, &C)) != MP_OKAY) { - goto LBL_ERR; - } - if ((res = mp_div_2 (&D, &D)) != MP_OKAY) { - goto LBL_ERR; - } - } + if ((res = mp_div_2(&D, &D)) != MP_OKAY) { + goto LBL_ERR; + } + } - /* 6. if u >= v then */ - if (mp_cmp (&u, &v) != MP_LT) { - /* u = u - v, A = A - C, B = B - D */ - if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) { - goto LBL_ERR; - } + /* 6. if u >= v then */ + if (mp_cmp(&u, &v) != MP_LT) { + /* u = u - v, A = A - C, B = B - D */ + if ((res = mp_sub(&u, &v, &u)) != MP_OKAY) { + goto LBL_ERR; + } - if ((res = mp_sub (&A, &C, &A)) != MP_OKAY) { - goto LBL_ERR; - } + if ((res = mp_sub(&A, &C, &A)) != MP_OKAY) { + goto LBL_ERR; + } - if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) { - goto LBL_ERR; - } - } else { - /* v - v - u, C = C - A, D = D - B */ - if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) { - goto LBL_ERR; - } + if ((res = mp_sub(&B, &D, &B)) != MP_OKAY) { + goto LBL_ERR; + } + } else { + /* v - v - u, C = C - A, D = D - B */ + if ((res = mp_sub(&v, &u, &v)) != MP_OKAY) { + goto LBL_ERR; + } - if ((res = mp_sub (&C, &A, &C)) != MP_OKAY) { - goto LBL_ERR; - } + if ((res = mp_sub(&C, &A, &C)) != MP_OKAY) { + goto LBL_ERR; + } - if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) { - goto LBL_ERR; - } - } + if ((res = mp_sub(&D, &B, &D)) != MP_OKAY) { + goto LBL_ERR; + } + } - /* if not zero goto step 4 */ - if (mp_iszero (&u) == MP_NO) - goto top; + /* if not zero goto step 4 */ + if (mp_iszero(&u) == MP_NO) + goto top; - /* now a = C, b = D, gcd == g*v */ + /* now a = C, b = D, gcd == g*v */ - /* if v != 1 then there is no inverse */ - if (mp_cmp_d (&v, 1) != MP_EQ) { - res = MP_VAL; - goto LBL_ERR; - } + /* if v != 1 then there is no inverse */ + if (mp_cmp_d(&v, 1) != MP_EQ) { + res = MP_VAL; + goto LBL_ERR; + } - /* if its too low */ - while (mp_cmp_d(&C, 0) == MP_LT) { + /* if its too low */ + while (mp_cmp_d(&C, 0) == MP_LT) { if ((res = mp_add(&C, b, &C)) != MP_OKAY) { goto LBL_ERR; } - } - - /* too big */ - while (mp_cmp_mag(&C, b) != MP_LT) { + } + + /* too big */ + while (mp_cmp_mag(&C, b) != MP_LT) { if ((res = mp_sub(&C, b, &C)) != MP_OKAY) { goto LBL_ERR; } - } - - /* C is now the inverse */ - mp_exch (&C, c); - res = MP_OKAY; -LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &A, &B, &C, &D, NULL); - return res; + } + + /* C is now the inverse */ + mp_exch(&C, c); + res = MP_OKAY; +LBL_ERR: + mp_clear_multi(&x, &y, &u, &v, &A, &B, &C, &D, NULL); + return res; } #endif |