Mercurial > dropbear
view libtommath/bn_mp_reduce_2k_l.c @ 1692:1051e4eea25a
Update LibTomMath to 1.2.0 (#84)
* update C files
* update other files
* update headers
* update makefiles
* remove mp_set/get_double()
* use ltm 1.2.0 API
* update ltm_desc
* use bundled tommath if system-tommath is too old
* XMALLOC etc. were changed to MP_MALLOC etc.
author | Steffen Jaeckel <s@jaeckel.eu> |
---|---|
date | Tue, 26 May 2020 17:36:47 +0200 |
parents | f52919ffd3b1 |
children |
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#include "tommath_private.h" #ifdef BN_MP_REDUCE_2K_L_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* reduces a modulo n where n is of the form 2**p - d This differs from reduce_2k since "d" can be larger than a single digit. */ mp_err mp_reduce_2k_l(mp_int *a, const mp_int *n, const mp_int *d) { mp_int q; mp_err err; int p; if ((err = mp_init(&q)) != MP_OKAY) { return err; } p = mp_count_bits(n); top: /* q = a/2**p, a = a mod 2**p */ if ((err = mp_div_2d(a, p, &q, a)) != MP_OKAY) { goto LBL_ERR; } /* q = q * d */ if ((err = mp_mul(&q, d, &q)) != MP_OKAY) { goto LBL_ERR; } /* a = a + q */ if ((err = s_mp_add(a, &q, a)) != MP_OKAY) { goto LBL_ERR; } if (mp_cmp_mag(a, n) != MP_LT) { if ((err = s_mp_sub(a, n, a)) != MP_OKAY) { goto LBL_ERR; } goto top; } LBL_ERR: mp_clear(&q); return err; } #endif