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comparison bn_mp_montgomery_setup.c @ 142:d29b64170cf0 libtommath-orig

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import of libtommath 0.32
author Matt Johnston <matt@ucc.asn.au>
date Sun, 19 Dec 2004 11:33:56 +0000
parents 86e0b50a9b58
children
comparison
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19:e1037a1e12e7 142:d29b64170cf0
1 #include <tommath.h>
2 #ifdef BN_MP_MONTGOMERY_SETUP_C
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
2 * 4 *
3 * LibTomMath is a library that provides multiple-precision 5 * LibTomMath is a library that provides multiple-precision
4 * integer arithmetic as well as number theoretic functionality. 6 * integer arithmetic as well as number theoretic functionality.
5 * 7 *
10 * The library is free for all purposes without any express 12 * The library is free for all purposes without any express
11 * guarantee it works. 13 * guarantee it works.
12 * 14 *
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org 15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
14 */ 16 */
15 #include <tommath.h>
16 17
17 /* setups the montgomery reduction stuff */ 18 /* setups the montgomery reduction stuff */
18 int 19 int
19 mp_montgomery_setup (mp_int * n, mp_digit * rho) 20 mp_montgomery_setup (mp_int * n, mp_digit * rho)
20 { 21 {
45 #ifdef MP_64BIT 46 #ifdef MP_64BIT
46 x *= 2 - b * x; /* here x*a==1 mod 2**64 */ 47 x *= 2 - b * x; /* here x*a==1 mod 2**64 */
47 #endif 48 #endif
48 49
49 /* rho = -1/m mod b */ 50 /* rho = -1/m mod b */
50 *rho = (((mp_digit) 1 << ((mp_digit) DIGIT_BIT)) - x) & MP_MASK; 51 *rho = (((mp_word)1 << ((mp_word) DIGIT_BIT)) - x) & MP_MASK;
51 52
52 return MP_OKAY; 53 return MP_OKAY;
53 } 54 }
55 #endif