diff options
Diffstat (limited to 'libtommath/bn_mp_karatsuba_mul.c')
| -rw-r--r-- | libtommath/bn_mp_karatsuba_mul.c | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/libtommath/bn_mp_karatsuba_mul.c b/libtommath/bn_mp_karatsuba_mul.c index daa78c7..a1ff713 100644 --- a/libtommath/bn_mp_karatsuba_mul.c +++ b/libtommath/bn_mp_karatsuba_mul.c @@ -26,12 +26,12 @@ * b = b1 * B**n + b0 * * Then, a * b => - a1b1 * B**2n + ((a1 - a0)(b1 - b0) + a0b0 + a1b1) * B + a0b0 + a1b1 * B**2n + ((a1 + a0)(b1 + b0) - (a0b0 + a1b1)) * B + a0b0 * * Note that a1b1 and a0b0 are used twice and only need to be * computed once. So in total three half size (half # of * digit) multiplications are performed, a0b0, a1b1 and - * (a1-b1)(a0-b0) + * (a1+b1)(a0+b0) * * Note that a multiplication of half the digits requires * 1/4th the number of single precision multiplications so in @@ -122,19 +122,19 @@ int mp_karatsuba_mul (mp_int * a, mp_int * b, mp_int * c) if (mp_mul (&x1, &y1, &x1y1) != MP_OKAY) goto X1Y1; /* x1y1 = x1*y1 */ - /* now calc x1-x0 and y1-y0 */ - if (mp_sub (&x1, &x0, &t1) != MP_OKAY) + /* now calc x1+x0 and y1+y0 */ + if (s_mp_add (&x1, &x0, &t1) != MP_OKAY) goto X1Y1; /* t1 = x1 - x0 */ - if (mp_sub (&y1, &y0, &x0) != MP_OKAY) + if (s_mp_add (&y1, &y0, &x0) != MP_OKAY) goto X1Y1; /* t2 = y1 - y0 */ if (mp_mul (&t1, &x0, &t1) != MP_OKAY) - goto X1Y1; /* t1 = (x1 - x0) * (y1 - y0) */ + goto X1Y1; /* t1 = (x1 + x0) * (y1 + y0) */ /* add x0y0 */ if (mp_add (&x0y0, &x1y1, &x0) != MP_OKAY) goto X1Y1; /* t2 = x0y0 + x1y1 */ - if (mp_sub (&x0, &t1, &t1) != MP_OKAY) - goto X1Y1; /* t1 = x0y0 + x1y1 - (x1-x0)*(y1-y0) */ + if (s_mp_sub (&t1, &x0, &t1) != MP_OKAY) + goto X1Y1; /* t1 = (x1+x0)*(y1+y0) - (x1y1 + x0y0) */ /* shift by B */ if (mp_lshd (&t1, B) != MP_OKAY) @@ -161,3 +161,7 @@ ERR: return err; } #endif + +/* $Source: /root/tcl/repos-to-convert/tcl/libtommath/bn_mp_karatsuba_mul.c,v $ */ +/* $Revision: 1.1.1.2 $ */ +/* $Date: 2005/09/26 16:31:56 $ */ |