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comparison libtommath/bn_s_mp_mul_digs.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_S_MP_MUL_DIGS_C 2 #ifdef BN_S_MP_MUL_DIGS_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 /* multiplies |a| * |b| and only computes upto digs digits of result 15 /* multiplies |a| * |b| and only computes upto digs digits of result
19 * HAC pp. 595, Algorithm 14.12 Modified so you can control how 16 * HAC pp. 595, Algorithm 14.12 Modified so you can control how
20 * many digits of output are created. 17 * many digits of output are created.
21 */ 18 */
22 int s_mp_mul_digs (mp_int * a, mp_int * b, mp_int * c, int digs) 19 int s_mp_mul_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs)
23 { 20 {
24 mp_int t; 21 mp_int t;
25 int res, pa, pb, ix, iy; 22 int res, pa, pb, ix, iy;
26 mp_digit u; 23 mp_digit u;
27 mp_word r; 24 mp_word r;
28 mp_digit tmpx, *tmpt, *tmpy; 25 mp_digit tmpx, *tmpt, *tmpy;
29 26
30 /* can we use the fast multiplier? */ 27 /* can we use the fast multiplier? */
31 if (((digs) < MP_WARRAY) && 28 if ((digs < (int)MP_WARRAY) &&
32 (MIN (a->used, b->used) < 29 (MIN(a->used, b->used) <
33 (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) { 30 (int)(1u << (((size_t)CHAR_BIT * sizeof(mp_word)) - (2u * (size_t)DIGIT_BIT))))) {
34 return fast_s_mp_mul_digs (a, b, c, digs); 31 return fast_s_mp_mul_digs(a, b, c, digs);
35 } 32 }
36 33
37 if ((res = mp_init_size (&t, digs)) != MP_OKAY) { 34 if ((res = mp_init_size(&t, digs)) != MP_OKAY) {
38 return res; 35 return res;
39 } 36 }
40 t.used = digs; 37 t.used = digs;
41 38
42 /* compute the digits of the product directly */ 39 /* compute the digits of the product directly */
43 pa = a->used; 40 pa = a->used;
44 for (ix = 0; ix < pa; ix++) { 41 for (ix = 0; ix < pa; ix++) {
45 /* set the carry to zero */ 42 /* set the carry to zero */
46 u = 0; 43 u = 0;
47 44
48 /* limit ourselves to making digs digits of output */ 45 /* limit ourselves to making digs digits of output */
49 pb = MIN (b->used, digs - ix); 46 pb = MIN(b->used, digs - ix);
50 47
51 /* setup some aliases */ 48 /* setup some aliases */
52 /* copy of the digit from a used within the nested loop */ 49 /* copy of the digit from a used within the nested loop */
53 tmpx = a->dp[ix]; 50 tmpx = a->dp[ix];
54
55 /* an alias for the destination shifted ix places */
56 tmpt = t.dp + ix;
57
58 /* an alias for the digits of b */
59 tmpy = b->dp;
60 51
61 /* compute the columns of the output and propagate the carry */ 52 /* an alias for the destination shifted ix places */
62 for (iy = 0; iy < pb; iy++) { 53 tmpt = t.dp + ix;
63 /* compute the column as a mp_word */
64 r = (mp_word)*tmpt +
65 ((mp_word)tmpx * (mp_word)*tmpy++) +
66 (mp_word)u;
67 54
68 /* the new column is the lower part of the result */ 55 /* an alias for the digits of b */
69 *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); 56 tmpy = b->dp;
70 57
71 /* get the carry word from the result */ 58 /* compute the columns of the output and propagate the carry */
72 u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); 59 for (iy = 0; iy < pb; iy++) {
73 } 60 /* compute the column as a mp_word */
74 /* set carry if it is placed below digs */ 61 r = (mp_word)*tmpt +
75 if ((ix + iy) < digs) { 62 ((mp_word)tmpx * (mp_word)*tmpy++) +
76 *tmpt = u; 63 (mp_word)u;
77 }
78 }
79 64
80 mp_clamp (&t); 65 /* the new column is the lower part of the result */
81 mp_exch (&t, c); 66 *tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
82 67
83 mp_clear (&t); 68 /* get the carry word from the result */
84 return MP_OKAY; 69 u = (mp_digit)(r >> (mp_word)DIGIT_BIT);
70 }
71 /* set carry if it is placed below digs */
72 if ((ix + iy) < digs) {
73 *tmpt = u;
74 }
75 }
76
77 mp_clamp(&t);
78 mp_exch(&t, c);
79
80 mp_clear(&t);
81 return MP_OKAY;
85 } 82 }
86 #endif 83 #endif
87 84
88 /* ref: $Format:%D$ */ 85 /* ref: HEAD -> master, tag: v1.1.0 */
89 /* git commit: $Format:%H$ */ 86 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
90 /* commit time: $Format:%ai$ */ 87 /* commit time: 2019-01-28 20:32:32 +0100 */