diff options
Diffstat (limited to 'libtommath/bn_s_mp_toom_sqr.c')
| -rw-r--r-- | libtommath/bn_s_mp_toom_sqr.c | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/libtommath/bn_s_mp_toom_sqr.c b/libtommath/bn_s_mp_toom_sqr.c new file mode 100644 index 0000000..f2ffb30 --- /dev/null +++ b/libtommath/bn_s_mp_toom_sqr.c @@ -0,0 +1,147 @@ +#include "tommath_private.h" +#ifdef BN_S_MP_TOOM_SQR_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ + +/* squaring using Toom-Cook 3-way algorithm */ + +/* + This file contains code from J. Arndt's book "Matters Computational" + and the accompanying FXT-library with permission of the author. +*/ + +/* squaring using Toom-Cook 3-way algorithm */ +/* + Setup and interpolation from algorithm SQR_3 in + + Chung, Jaewook, and M. Anwar Hasan. "Asymmetric squaring formulae." + 18th IEEE Symposium on Computer Arithmetic (ARITH'07). IEEE, 2007. + +*/ +mp_err s_mp_toom_sqr(const mp_int *a, mp_int *b) +{ + mp_int S0, a0, a1, a2; + mp_digit *tmpa, *tmpc; + int B, count; + mp_err err; + + + /* init temps */ + if ((err = mp_init(&S0)) != MP_OKAY) { + return err; + } + + /* B */ + B = a->used / 3; + + /** a = a2 * x^2 + a1 * x + a0; */ + if ((err = mp_init_size(&a0, B)) != MP_OKAY) goto LBL_ERRa0; + + a0.used = B; + if ((err = mp_init_size(&a1, B)) != MP_OKAY) goto LBL_ERRa1; + a1.used = B; + if ((err = mp_init_size(&a2, B + (a->used - (3 * B)))) != MP_OKAY) goto LBL_ERRa2; + + tmpa = a->dp; + tmpc = a0.dp; + for (count = 0; count < B; count++) { + *tmpc++ = *tmpa++; + } + tmpc = a1.dp; + for (; count < (2 * B); count++) { + *tmpc++ = *tmpa++; + } + tmpc = a2.dp; + for (; count < a->used; count++) { + *tmpc++ = *tmpa++; + a2.used++; + } + mp_clamp(&a0); + mp_clamp(&a1); + mp_clamp(&a2); + + /** S0 = a0^2; */ + if ((err = mp_sqr(&a0, &S0)) != MP_OKAY) goto LBL_ERR; + + /** \\S1 = (a2 + a1 + a0)^2 */ + /** \\S2 = (a2 - a1 + a0)^2 */ + /** \\S1 = a0 + a2; */ + /** a0 = a0 + a2; */ + if ((err = mp_add(&a0, &a2, &a0)) != MP_OKAY) goto LBL_ERR; + /** \\S2 = S1 - a1; */ + /** b = a0 - a1; */ + if ((err = mp_sub(&a0, &a1, b)) != MP_OKAY) goto LBL_ERR; + /** \\S1 = S1 + a1; */ + /** a0 = a0 + a1; */ + if ((err = mp_add(&a0, &a1, &a0)) != MP_OKAY) goto LBL_ERR; + /** \\S1 = S1^2; */ + /** a0 = a0^2; */ + if ((err = mp_sqr(&a0, &a0)) != MP_OKAY) goto LBL_ERR; + /** \\S2 = S2^2; */ + /** b = b^2; */ + if ((err = mp_sqr(b, b)) != MP_OKAY) goto LBL_ERR; + + /** \\ S3 = 2 * a1 * a2 */ + /** \\S3 = a1 * a2; */ + /** a1 = a1 * a2; */ + if ((err = mp_mul(&a1, &a2, &a1)) != MP_OKAY) goto LBL_ERR; + /** \\S3 = S3 << 1; */ + /** a1 = a1 << 1; */ + if ((err = mp_mul_2(&a1, &a1)) != MP_OKAY) goto LBL_ERR; + + /** \\S4 = a2^2; */ + /** a2 = a2^2; */ + if ((err = mp_sqr(&a2, &a2)) != MP_OKAY) goto LBL_ERR; + + /** \\ tmp = (S1 + S2)/2 */ + /** \\tmp = S1 + S2; */ + /** b = a0 + b; */ + if ((err = mp_add(&a0, b, b)) != MP_OKAY) goto LBL_ERR; + /** \\tmp = tmp >> 1; */ + /** b = b >> 1; */ + if ((err = mp_div_2(b, b)) != MP_OKAY) goto LBL_ERR; + + /** \\ S1 = S1 - tmp - S3 */ + /** \\S1 = S1 - tmp; */ + /** a0 = a0 - b; */ + if ((err = mp_sub(&a0, b, &a0)) != MP_OKAY) goto LBL_ERR; + /** \\S1 = S1 - S3; */ + /** a0 = a0 - a1; */ + if ((err = mp_sub(&a0, &a1, &a0)) != MP_OKAY) goto LBL_ERR; + + /** \\S2 = tmp - S4 -S0 */ + /** \\S2 = tmp - S4; */ + /** b = b - a2; */ + if ((err = mp_sub(b, &a2, b)) != MP_OKAY) goto LBL_ERR; + /** \\S2 = S2 - S0; */ + /** b = b - S0; */ + if ((err = mp_sub(b, &S0, b)) != MP_OKAY) goto LBL_ERR; + + + /** \\P = S4*x^4 + S3*x^3 + S2*x^2 + S1*x + S0; */ + /** P = a2*x^4 + a1*x^3 + b*x^2 + a0*x + S0; */ + + if ((err = mp_lshd(&a2, 4 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_lshd(&a1, 3 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_lshd(b, 2 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_lshd(&a0, 1 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(&a2, &a1, &a2)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(&a2, b, b)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(b, &a0, b)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(b, &S0, b)) != MP_OKAY) goto LBL_ERR; + /** a^2 - P */ + + +LBL_ERR: + mp_clear(&a2); +LBL_ERRa2: + mp_clear(&a1); +LBL_ERRa1: + mp_clear(&a0); +LBL_ERRa0: + mp_clear(&S0); + + return err; +} + +#endif |