diff options
Diffstat (limited to 'libtommath/bn_mp_karatsuba_sqr.c')
-rw-r--r-- | libtommath/bn_mp_karatsuba_sqr.c | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/libtommath/bn_mp_karatsuba_sqr.c b/libtommath/bn_mp_karatsuba_sqr.c new file mode 100644 index 0000000..ae9a828 --- /dev/null +++ b/libtommath/bn_mp_karatsuba_sqr.c @@ -0,0 +1,121 @@ +#include <tommath.h> +#ifdef BN_MP_KARATSUBA_SQR_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis + * + * LibTomMath is a library that provides multiple-precision + * integer arithmetic as well as number theoretic functionality. + * + * The library was designed directly after the MPI library by + * Michael Fromberger but has been written from scratch with + * additional optimizations in place. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org + */ + +/* Karatsuba squaring, computes b = a*a using three + * half size squarings + * + * See comments of karatsuba_mul for details. It + * is essentially the same algorithm but merely + * tuned to perform recursive squarings. + */ +int mp_karatsuba_sqr (mp_int * a, mp_int * b) +{ + mp_int x0, x1, t1, t2, x0x0, x1x1; + int B, err; + + err = MP_MEM; + + /* min # of digits */ + B = a->used; + + /* now divide in two */ + B = B >> 1; + + /* init copy all the temps */ + if (mp_init_size (&x0, B) != MP_OKAY) + goto ERR; + if (mp_init_size (&x1, a->used - B) != MP_OKAY) + goto X0; + + /* init temps */ + if (mp_init_size (&t1, a->used * 2) != MP_OKAY) + goto X1; + if (mp_init_size (&t2, a->used * 2) != MP_OKAY) + goto T1; + if (mp_init_size (&x0x0, B * 2) != MP_OKAY) + goto T2; + if (mp_init_size (&x1x1, (a->used - B) * 2) != MP_OKAY) + goto X0X0; + + { + register int x; + register mp_digit *dst, *src; + + src = a->dp; + + /* now shift the digits */ + dst = x0.dp; + for (x = 0; x < B; x++) { + *dst++ = *src++; + } + + dst = x1.dp; + for (x = B; x < a->used; x++) { + *dst++ = *src++; + } + } + + x0.used = B; + x1.used = a->used - B; + + mp_clamp (&x0); + + /* now calc the products x0*x0 and x1*x1 */ + if (mp_sqr (&x0, &x0x0) != MP_OKAY) + goto X1X1; /* x0x0 = x0*x0 */ + if (mp_sqr (&x1, &x1x1) != MP_OKAY) + goto X1X1; /* x1x1 = x1*x1 */ + + /* now calc (x1+x0)**2 */ + if (s_mp_add (&x1, &x0, &t1) != MP_OKAY) + goto X1X1; /* t1 = x1 - x0 */ + if (mp_sqr (&t1, &t1) != MP_OKAY) + goto X1X1; /* t1 = (x1 - x0) * (x1 - x0) */ + + /* add x0y0 */ + if (s_mp_add (&x0x0, &x1x1, &t2) != MP_OKAY) + goto X1X1; /* t2 = x0x0 + x1x1 */ + if (s_mp_sub (&t1, &t2, &t1) != MP_OKAY) + goto X1X1; /* t1 = (x1+x0)**2 - (x0x0 + x1x1) */ + + /* shift by B */ + if (mp_lshd (&t1, B) != MP_OKAY) + goto X1X1; /* t1 = (x0x0 + x1x1 - (x1-x0)*(x1-x0))<<B */ + if (mp_lshd (&x1x1, B * 2) != MP_OKAY) + goto X1X1; /* x1x1 = x1x1 << 2*B */ + + if (mp_add (&x0x0, &t1, &t1) != MP_OKAY) + goto X1X1; /* t1 = x0x0 + t1 */ + if (mp_add (&t1, &x1x1, b) != MP_OKAY) + goto X1X1; /* t1 = x0x0 + t1 + x1x1 */ + + err = MP_OKAY; + +X1X1:mp_clear (&x1x1); +X0X0:mp_clear (&x0x0); +T2:mp_clear (&t2); +T1:mp_clear (&t1); +X1:mp_clear (&x1); +X0:mp_clear (&x0); +ERR: + return err; +} +#endif + +/* $Source: /root/tcl/repos-to-convert/tcl/libtommath/bn_mp_karatsuba_sqr.c,v $ */ +/* $Revision: 1.1.1.1.2.1 $ */ +/* $Date: 2005/09/26 20:16:53 $ */ |