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.
Diff: math/mont/fp_montgomery_setup.c
- Revision:
- 0:35aa5be3b78d
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/math/mont/fp_montgomery_setup.c Fri Jun 06 10:49:02 2014 +0000 @@ -0,0 +1,48 @@ +/* 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 $ */