A super trimmed down TLS stack, GPL licensed
Dependents: MiniTLS-HTTPS-Example
MiniTLS - A super trimmed down TLS/SSL Library for embedded devices Author: Donatien Garnier Copyright (C) 2013-2014 AppNearMe Ltd
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
math/mont/fp_montgomery_setup.c
- Committer:
- MiniTLS
- Date:
- 2014-06-06
- Revision:
- 0:35aa5be3b78d
File content as of revision 0:35aa5be3b78d:
/* TomsFastMath, a fast ISO C bignum library. * * This project is meant to fill in where LibTomMath * falls short. That is speed ;-) * * This project is public domain and free for all purposes. * * Tom St Denis, tomstdenis@gmail.com */ #include <tfm.h> /* setups the montgomery reduction */ int fp_montgomery_setup(fp_int *a, fp_digit *rho) { fp_digit x, b; /* fast inversion mod 2**k * * Based on the fact that * * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) * => 2*X*A - X*X*A*A = 1 * => 2*(1) - (1) = 1 */ b = a->dp[0]; if ((b & 1) == 0) { return FP_VAL; } x = (((b + 2) & 4) << 1) + b; /* here x*a==1 mod 2**4 */ x *= 2 - b * x; /* here x*a==1 mod 2**8 */ x *= 2 - b * x; /* here x*a==1 mod 2**16 */ x *= 2 - b * x; /* here x*a==1 mod 2**32 */ #ifdef FP_64BIT x *= 2 - b * x; /* here x*a==1 mod 2**64 */ #endif /* rho = -1/m mod b */ *rho = (((fp_word) 1 << ((fp_word) DIGIT_BIT)) - ((fp_word)x)); return FP_OKAY; } /* $Source: /cvs/libtom/tomsfastmath/src/mont/fp_montgomery_setup.c,v $ */ /* $Revision: 1.1 $ */ /* $Date: 2006/12/31 21:25:53 $ */