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author | The Android Open Source Project <initial-contribution@android.com> | 2009-03-03 18:28:21 -0800 |
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committer | The Android Open Source Project <initial-contribution@android.com> | 2009-03-03 18:28:21 -0800 |
commit | 4992dc5127843624d3deb2d54af917a7ec50fb45 (patch) | |
tree | 0cbcf7d3a36648aec263dcd0744dc5231e7a6844 /libtommath/bn_mp_dr_reduce.c | |
parent | 1abbfe5d373a44e7e0525fb7971ef0e00955f2e4 (diff) | |
download | dropbear-4992dc5127843624d3deb2d54af917a7ec50fb45.tar.gz |
auto import from //depot/cupcake/@135843
Diffstat (limited to 'libtommath/bn_mp_dr_reduce.c')
-rw-r--r-- | libtommath/bn_mp_dr_reduce.c | 94 |
1 files changed, 0 insertions, 94 deletions
diff --git a/libtommath/bn_mp_dr_reduce.c b/libtommath/bn_mp_dr_reduce.c deleted file mode 100644 index d2ef18f..0000000 --- a/libtommath/bn_mp_dr_reduce.c +++ /dev/null @@ -1,94 +0,0 @@ -#include <tommath.h> -#ifdef BN_MP_DR_REDUCE_C -/* LibTomMath, multiple-precision integer library -- Tom St Denis - * - * LibTomMath is a library that provides multiple-precision - * integer arithmetic as well as number theoretic functionality. - * - * The library was designed directly after the MPI library by - * 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, tomstdenis@gmail.com, http://math.libtomcrypt.com - */ - -/* reduce "x" in place modulo "n" using the Diminished Radix algorithm. - * - * Based on algorithm from the paper - * - * "Generating Efficient Primes for Discrete Log Cryptosystems" - * Chae Hoon Lim, Pil Joong Lee, - * POSTECH Information Research Laboratories - * - * The modulus must be of a special format [see manual] - * - * Has been modified to use algorithm 7.10 from the LTM book instead - * - * Input x must be in the range 0 <= x <= (n-1)**2 - */ -int -mp_dr_reduce (mp_int * x, mp_int * n, mp_digit k) -{ - int err, i, m; - mp_word r; - mp_digit mu, *tmpx1, *tmpx2; - - /* m = digits in modulus */ - m = n->used; - - /* ensure that "x" has at least 2m digits */ - if (x->alloc < m + m) { - if ((err = mp_grow (x, m + m)) != MP_OKAY) { - return err; - } - } - -/* top of loop, this is where the code resumes if - * another reduction pass is required. - */ -top: - /* aliases for digits */ - /* alias for lower half of x */ - tmpx1 = x->dp; - - /* alias for upper half of x, or x/B**m */ - tmpx2 = x->dp + m; - - /* set carry to zero */ - mu = 0; - - /* compute (x mod B**m) + k * [x/B**m] inline and inplace */ - for (i = 0; i < m; i++) { - r = ((mp_word)*tmpx2++) * ((mp_word)k) + *tmpx1 + mu; - *tmpx1++ = (mp_digit)(r & MP_MASK); - mu = (mp_digit)(r >> ((mp_word)DIGIT_BIT)); - } - - /* set final carry */ - *tmpx1++ = mu; - - /* zero words above m */ - for (i = m + 1; i < x->used; i++) { - *tmpx1++ = 0; - } - - /* clamp, sub and return */ - mp_clamp (x); - - /* if x >= n then subtract and reduce again - * Each successive "recursion" makes the input smaller and smaller. - */ - if (mp_cmp_mag (x, n) != MP_LT) { - s_mp_sub(x, n, x); - goto top; - } - return MP_OKAY; -} -#endif - -/* $Source: /cvs/libtom/libtommath/bn_mp_dr_reduce.c,v $ */ -/* $Revision: 1.3 $ */ -/* $Date: 2006/03/31 14:18:44 $ */ |