diff options
Diffstat (limited to 'libtommath/bn_mp_jacobi.c')
| -rw-r--r-- | libtommath/bn_mp_jacobi.c | 44 |
1 files changed, 28 insertions, 16 deletions
diff --git a/libtommath/bn_mp_jacobi.c b/libtommath/bn_mp_jacobi.c index 07a9d65..3c114e3 100644 --- a/libtommath/bn_mp_jacobi.c +++ b/libtommath/bn_mp_jacobi.c @@ -1,4 +1,4 @@ -#include <tommath.h> +#include <tommath_private.h> #ifdef BN_MP_JACOBI_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * @@ -12,27 +12,39 @@ * The library is free for all purposes without any express * guarantee it works. * - * Tom St Denis, tomstdenis@gmail.com, http://libtom.org + * Tom St Denis, tstdenis82@gmail.com, http://libtom.org */ /* computes the jacobi c = (a | n) (or Legendre if n is prime) * HAC pp. 73 Algorithm 2.149 + * HAC is wrong here, as the special case of (0 | 1) is not + * handled correctly. */ -int mp_jacobi (mp_int * a, mp_int * p, int *c) +int mp_jacobi (mp_int * a, mp_int * n, int *c) { mp_int a1, p1; int k, s, r, res; mp_digit residue; - /* if p <= 0 return MP_VAL */ - if (mp_cmp_d(p, 0) != MP_GT) { + /* if a < 0 return MP_VAL */ + if (mp_isneg(a) == MP_YES) { return MP_VAL; } - /* step 1. if a == 0, return 0 */ - if (mp_iszero (a) == 1) { - *c = 0; - return MP_OKAY; + /* if n <= 0 return MP_VAL */ + if (mp_cmp_d(n, 0) != MP_GT) { + return MP_VAL; + } + + /* step 1. handle case of a == 0 */ + if (mp_iszero (a) == MP_YES) { + /* special case of a == 0 and n == 1 */ + if (mp_cmp_d (n, 1) == MP_EQ) { + *c = 1; + } else { + *c = 0; + } + return MP_OKAY; } /* step 2. if a == 1, return 1 */ @@ -64,17 +76,17 @@ int mp_jacobi (mp_int * a, mp_int * p, int *c) s = 1; } else { /* else set s=1 if p = 1/7 (mod 8) or s=-1 if p = 3/5 (mod 8) */ - residue = p->dp[0] & 7; + residue = n->dp[0] & 7; - if (residue == 1 || residue == 7) { + if ((residue == 1) || (residue == 7)) { s = 1; - } else if (residue == 3 || residue == 5) { + } else if ((residue == 3) || (residue == 5)) { s = -1; } } /* step 5. if p == 3 (mod 4) *and* a1 == 3 (mod 4) then s = -s */ - if ( ((p->dp[0] & 3) == 3) && ((a1.dp[0] & 3) == 3)) { + if ( ((n->dp[0] & 3) == 3) && ((a1.dp[0] & 3) == 3)) { s = -s; } @@ -83,7 +95,7 @@ int mp_jacobi (mp_int * a, mp_int * p, int *c) *c = s; } else { /* n1 = n mod a1 */ - if ((res = mp_mod (p, &a1, &p1)) != MP_OKAY) { + if ((res = mp_mod (n, &a1, &p1)) != MP_OKAY) { goto LBL_P1; } if ((res = mp_jacobi (&p1, &a1, &r)) != MP_OKAY) { @@ -101,5 +113,5 @@ LBL_A1:mp_clear (&a1); #endif /* $Source$ */ -/* $Revision: 0.41 $ */ -/* $Date: 2007-04-18 09:58:18 +0000 $ */ +/* $Revision$ */ +/* $Date$ */ |