Mercurial > dropbear
comparison libtommath/bn_mp_montgomery_setup.c @ 1655:f52919ffd3b1
update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
* make key-generation compliant to FIPS 186.4
* fix includes in tommath_class.h
* update fuzzcorpus instead of error-out
* fixup fuzzing make-targets
* update Makefile.in
* apply necessary patches to ltm sources
* clean-up not required ltm files
* update to vanilla ltm 1.1.0
this already only contains the required files
* remove set/get double
author | Steffen Jaeckel <s_jaeckel@gmx.de> |
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date | Mon, 16 Sep 2019 15:50:38 +0200 |
parents | 8bba51a55704 |
children | 1051e4eea25a |
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1654:cc0fc5131c5c | 1655:f52919ffd3b1 |
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1 #include <tommath_private.h> | 1 #include "tommath_private.h" |
2 #ifdef BN_MP_MONTGOMERY_SETUP_C | 2 #ifdef BN_MP_MONTGOMERY_SETUP_C |
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis | 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
4 * | 4 * |
5 * LibTomMath is a library that provides multiple-precision | 5 * LibTomMath is a library that provides multiple-precision |
6 * integer arithmetic as well as number theoretic functionality. | 6 * integer arithmetic as well as number theoretic functionality. |
7 * | 7 * |
8 * The library was designed directly after the MPI library by | 8 * The library was designed directly after the MPI library by |
9 * Michael Fromberger but has been written from scratch with | 9 * Michael Fromberger but has been written from scratch with |
10 * additional optimizations in place. | 10 * additional optimizations in place. |
11 * | 11 * |
12 * The library is free for all purposes without any express | 12 * SPDX-License-Identifier: Unlicense |
13 * guarantee it works. | |
14 * | |
15 * Tom St Denis, [email protected], http://libtom.org | |
16 */ | 13 */ |
17 | 14 |
18 /* setups the montgomery reduction stuff */ | 15 /* setups the montgomery reduction stuff */ |
19 int | 16 int mp_montgomery_setup(const mp_int *n, mp_digit *rho) |
20 mp_montgomery_setup (mp_int * n, mp_digit * rho) | |
21 { | 17 { |
22 mp_digit x, b; | 18 mp_digit x, b; |
23 | 19 |
24 /* fast inversion mod 2**k | 20 /* fast inversion mod 2**k |
25 * | 21 * |
26 * Based on the fact that | 22 * Based on the fact that |
27 * | 23 * |
28 * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) | 24 * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) |
29 * => 2*X*A - X*X*A*A = 1 | 25 * => 2*X*A - X*X*A*A = 1 |
30 * => 2*(1) - (1) = 1 | 26 * => 2*(1) - (1) = 1 |
31 */ | 27 */ |
32 b = n->dp[0]; | 28 b = n->dp[0]; |
33 | 29 |
34 if ((b & 1) == 0) { | 30 if ((b & 1u) == 0u) { |
35 return MP_VAL; | 31 return MP_VAL; |
36 } | 32 } |
37 | 33 |
38 x = (((b + 2) & 4) << 1) + b; /* here x*a==1 mod 2**4 */ | 34 x = (((b + 2u) & 4u) << 1) + b; /* here x*a==1 mod 2**4 */ |
39 x *= 2 - (b * x); /* here x*a==1 mod 2**8 */ | 35 x *= 2u - (b * x); /* here x*a==1 mod 2**8 */ |
40 #if !defined(MP_8BIT) | 36 #if !defined(MP_8BIT) |
41 x *= 2 - (b * x); /* here x*a==1 mod 2**16 */ | 37 x *= 2u - (b * x); /* here x*a==1 mod 2**16 */ |
42 #endif | 38 #endif |
43 #if defined(MP_64BIT) || !(defined(MP_8BIT) || defined(MP_16BIT)) | 39 #if defined(MP_64BIT) || !(defined(MP_8BIT) || defined(MP_16BIT)) |
44 x *= 2 - (b * x); /* here x*a==1 mod 2**32 */ | 40 x *= 2u - (b * x); /* here x*a==1 mod 2**32 */ |
45 #endif | 41 #endif |
46 #ifdef MP_64BIT | 42 #ifdef MP_64BIT |
47 x *= 2 - (b * x); /* here x*a==1 mod 2**64 */ | 43 x *= 2u - (b * x); /* here x*a==1 mod 2**64 */ |
48 #endif | 44 #endif |
49 | 45 |
50 /* rho = -1/m mod b */ | 46 /* rho = -1/m mod b */ |
51 *rho = (mp_digit)(((mp_word)1 << ((mp_word) DIGIT_BIT)) - x) & MP_MASK; | 47 *rho = (mp_digit)(((mp_word)1 << (mp_word)DIGIT_BIT) - x) & MP_MASK; |
52 | 48 |
53 return MP_OKAY; | 49 return MP_OKAY; |
54 } | 50 } |
55 #endif | 51 #endif |
56 | 52 |
57 /* ref: $Format:%D$ */ | 53 /* ref: HEAD -> master, tag: v1.1.0 */ |
58 /* git commit: $Format:%H$ */ | 54 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ |
59 /* commit time: $Format:%ai$ */ | 55 /* commit time: 2019-01-28 20:32:32 +0100 */ |