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comparison libtommath/bn_mp_rshd.c @ 1655:f52919ffd3b1

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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>
date Mon, 16 Sep 2019 15:50:38 +0200
parents 8bba51a55704
children 1051e4eea25a
comparison
equal deleted inserted replaced
1654:cc0fc5131c5c 1655:f52919ffd3b1
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_RSHD_C 2 #ifdef BN_MP_RSHD_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 /* shift right a certain amount of digits */ 15 /* shift right a certain amount of digits */
19 void mp_rshd (mp_int * a, int b) 16 void mp_rshd(mp_int *a, int b)
20 { 17 {
21 int x; 18 int x;
22 19
23 /* if b <= 0 then ignore it */ 20 /* if b <= 0 then ignore it */
24 if (b <= 0) { 21 if (b <= 0) {
25 return; 22 return;
26 } 23 }
27 24
28 /* if b > used then simply zero it and return */ 25 /* if b > used then simply zero it and return */
29 if (a->used <= b) { 26 if (a->used <= b) {
30 mp_zero (a); 27 mp_zero(a);
31 return; 28 return;
32 } 29 }
33 30
34 { 31 {
35 mp_digit *bottom, *top; 32 mp_digit *bottom, *top;
36 33
37 /* shift the digits down */ 34 /* shift the digits down */
38 35
39 /* bottom */ 36 /* bottom */
40 bottom = a->dp; 37 bottom = a->dp;
41 38
42 /* top [offset into digits] */ 39 /* top [offset into digits] */
43 top = a->dp + b; 40 top = a->dp + b;
44 41
45 /* this is implemented as a sliding window where 42 /* this is implemented as a sliding window where
46 * the window is b-digits long and digits from 43 * the window is b-digits long and digits from
47 * the top of the window are copied to the bottom 44 * the top of the window are copied to the bottom
48 * 45 *
49 * e.g. 46 * e.g.
50 47
51 b-2 | b-1 | b0 | b1 | b2 | ... | bb | ----> 48 b-2 | b-1 | b0 | b1 | b2 | ... | bb | ---->
52 /\ | ----> 49 /\ | ---->
53 \-------------------/ ----> 50 \-------------------/ ---->
54 */ 51 */
55 for (x = 0; x < (a->used - b); x++) { 52 for (x = 0; x < (a->used - b); x++) {
56 *bottom++ = *top++; 53 *bottom++ = *top++;
57 } 54 }
58 55
59 /* zero the top digits */ 56 /* zero the top digits */
60 for (; x < a->used; x++) { 57 for (; x < a->used; x++) {
61 *bottom++ = 0; 58 *bottom++ = 0;
62 } 59 }
63 } 60 }
64 61
65 /* remove excess digits */ 62 /* remove excess digits */
66 a->used -= b; 63 a->used -= b;
67 } 64 }
68 #endif 65 #endif
69 66
70 /* ref: $Format:%D$ */ 67 /* ref: HEAD -> master, tag: v1.1.0 */
71 /* git commit: $Format:%H$ */ 68 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
72 /* commit time: $Format:%ai$ */ 69 /* commit time: 2019-01-28 20:32:32 +0100 */