Mercurial > dropbear
diff libtommath/bn_fast_mp_montgomery_reduce.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> |
---|---|
date | Mon, 16 Sep 2019 15:50:38 +0200 |
parents | 8bba51a55704 |
children |
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--- a/libtommath/bn_fast_mp_montgomery_reduce.c Wed May 15 21:59:45 2019 +0800 +++ b/libtommath/bn_fast_mp_montgomery_reduce.c Mon Sep 16 15:50:38 2019 +0200 @@ -1,4 +1,4 @@ -#include <tommath_private.h> +#include "tommath_private.h" #ifdef BN_FAST_MP_MONTGOMERY_REDUCE_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * @@ -9,10 +9,7 @@ * Michael Fromberger but has been written from scratch with * additional optimizations in place. * - * The library is free for all purposes without any express - * guarantee it works. - * - * Tom St Denis, [email protected], http://libtom.org + * SPDX-License-Identifier: Unlicense */ /* computes xR**-1 == x (mod N) via Montgomery Reduction @@ -23,150 +20,154 @@ * * Based on Algorithm 14.32 on pp.601 of HAC. */ -int fast_mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho) +int fast_mp_montgomery_reduce(mp_int *x, const mp_int *n, mp_digit rho) { - int ix, res, olduse; - mp_word W[MP_WARRAY]; + int ix, res, olduse; + mp_word W[MP_WARRAY]; - /* get old used count */ - olduse = x->used; + if (x->used > (int)MP_WARRAY) { + return MP_VAL; + } - /* grow a as required */ - if (x->alloc < (n->used + 1)) { - if ((res = mp_grow (x, n->used + 1)) != MP_OKAY) { - return res; - } - } + /* get old used count */ + olduse = x->used; - /* first we have to get the digits of the input into - * an array of double precision words W[...] - */ - { - mp_word *_W; - mp_digit *tmpx; + /* grow a as required */ + if (x->alloc < (n->used + 1)) { + if ((res = mp_grow(x, n->used + 1)) != MP_OKAY) { + return res; + } + } - /* alias for the W[] array */ - _W = W; - - /* alias for the digits of x*/ - tmpx = x->dp; - - /* copy the digits of a into W[0..a->used-1] */ - for (ix = 0; ix < x->used; ix++) { - *_W++ = *tmpx++; - } + /* first we have to get the digits of the input into + * an array of double precision words W[...] + */ + { + mp_word *_W; + mp_digit *tmpx; - /* zero the high words of W[a->used..m->used*2] */ - for (; ix < ((n->used * 2) + 1); ix++) { - *_W++ = 0; - } - } + /* alias for the W[] array */ + _W = W; - /* now we proceed to zero successive digits - * from the least significant upwards - */ - for (ix = 0; ix < n->used; ix++) { - /* mu = ai * m' mod b - * - * We avoid a double precision multiplication (which isn't required) - * by casting the value down to a mp_digit. Note this requires - * that W[ix-1] have the carry cleared (see after the inner loop) - */ - mp_digit mu; - mu = (mp_digit) (((W[ix] & MP_MASK) * rho) & MP_MASK); + /* alias for the digits of x*/ + tmpx = x->dp; + + /* copy the digits of a into W[0..a->used-1] */ + for (ix = 0; ix < x->used; ix++) { + *_W++ = *tmpx++; + } - /* a = a + mu * m * b**i - * - * This is computed in place and on the fly. The multiplication - * by b**i is handled by offseting which columns the results - * are added to. - * - * Note the comba method normally doesn't handle carries in the - * inner loop In this case we fix the carry from the previous - * column since the Montgomery reduction requires digits of the - * result (so far) [see above] to work. This is - * handled by fixing up one carry after the inner loop. The - * carry fixups are done in order so after these loops the - * first m->used words of W[] have the carries fixed - */ - { - int iy; - mp_digit *tmpn; - mp_word *_W; + /* zero the high words of W[a->used..m->used*2] */ + for (; ix < ((n->used * 2) + 1); ix++) { + *_W++ = 0; + } + } + + /* now we proceed to zero successive digits + * from the least significant upwards + */ + for (ix = 0; ix < n->used; ix++) { + /* mu = ai * m' mod b + * + * We avoid a double precision multiplication (which isn't required) + * by casting the value down to a mp_digit. Note this requires + * that W[ix-1] have the carry cleared (see after the inner loop) + */ + mp_digit mu; + mu = ((W[ix] & MP_MASK) * rho) & MP_MASK; - /* alias for the digits of the modulus */ - tmpn = n->dp; - - /* Alias for the columns set by an offset of ix */ - _W = W + ix; + /* a = a + mu * m * b**i + * + * This is computed in place and on the fly. The multiplication + * by b**i is handled by offseting which columns the results + * are added to. + * + * Note the comba method normally doesn't handle carries in the + * inner loop In this case we fix the carry from the previous + * column since the Montgomery reduction requires digits of the + * result (so far) [see above] to work. This is + * handled by fixing up one carry after the inner loop. The + * carry fixups are done in order so after these loops the + * first m->used words of W[] have the carries fixed + */ + { + int iy; + mp_digit *tmpn; + mp_word *_W; - /* inner loop */ - for (iy = 0; iy < n->used; iy++) { - *_W++ += ((mp_word)mu) * ((mp_word)*tmpn++); - } - } - - /* now fix carry for next digit, W[ix+1] */ - W[ix + 1] += W[ix] >> ((mp_word) DIGIT_BIT); - } + /* alias for the digits of the modulus */ + tmpn = n->dp; - /* now we have to propagate the carries and - * shift the words downward [all those least - * significant digits we zeroed]. - */ - { - mp_digit *tmpx; - mp_word *_W, *_W1; + /* Alias for the columns set by an offset of ix */ + _W = W + ix; + + /* inner loop */ + for (iy = 0; iy < n->used; iy++) { + *_W++ += (mp_word)mu * (mp_word)*tmpn++; + } + } - /* nox fix rest of carries */ + /* now fix carry for next digit, W[ix+1] */ + W[ix + 1] += W[ix] >> (mp_word)DIGIT_BIT; + } - /* alias for current word */ - _W1 = W + ix; + /* now we have to propagate the carries and + * shift the words downward [all those least + * significant digits we zeroed]. + */ + { + mp_digit *tmpx; + mp_word *_W, *_W1; - /* alias for next word, where the carry goes */ - _W = W + ++ix; + /* nox fix rest of carries */ - for (; ix <= ((n->used * 2) + 1); ix++) { - *_W++ += *_W1++ >> ((mp_word) DIGIT_BIT); - } + /* alias for current word */ + _W1 = W + ix; + + /* alias for next word, where the carry goes */ + _W = W + ++ix; + + for (; ix <= ((n->used * 2) + 1); ix++) { + *_W++ += *_W1++ >> (mp_word)DIGIT_BIT; + } - /* copy out, A = A/b**n - * - * The result is A/b**n but instead of converting from an - * array of mp_word to mp_digit than calling mp_rshd - * we just copy them in the right order - */ + /* copy out, A = A/b**n + * + * The result is A/b**n but instead of converting from an + * array of mp_word to mp_digit than calling mp_rshd + * we just copy them in the right order + */ - /* alias for destination word */ - tmpx = x->dp; - - /* alias for shifted double precision result */ - _W = W + n->used; + /* alias for destination word */ + tmpx = x->dp; - for (ix = 0; ix < (n->used + 1); ix++) { - *tmpx++ = (mp_digit)(*_W++ & ((mp_word) MP_MASK)); - } + /* alias for shifted double precision result */ + _W = W + n->used; + + for (ix = 0; ix < (n->used + 1); ix++) { + *tmpx++ = *_W++ & (mp_word)MP_MASK; + } - /* zero oldused digits, if the input a was larger than - * m->used+1 we'll have to clear the digits - */ - for (; ix < olduse; ix++) { - *tmpx++ = 0; - } - } + /* zero oldused digits, if the input a was larger than + * m->used+1 we'll have to clear the digits + */ + for (; ix < olduse; ix++) { + *tmpx++ = 0; + } + } - /* set the max used and clamp */ - x->used = n->used + 1; - mp_clamp (x); + /* set the max used and clamp */ + x->used = n->used + 1; + mp_clamp(x); - /* if A >= m then A = A - m */ - if (mp_cmp_mag (x, n) != MP_LT) { - return s_mp_sub (x, n, x); - } - return MP_OKAY; + /* if A >= m then A = A - m */ + if (mp_cmp_mag(x, n) != MP_LT) { + return s_mp_sub(x, n, x); + } + return MP_OKAY; } #endif -/* ref: $Format:%D$ */ -/* git commit: $Format:%H$ */ -/* commit time: $Format:%ai$ */ +/* ref: HEAD -> master, tag: v1.1.0 */ +/* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ +/* commit time: 2019-01-28 20:32:32 +0100 */