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-rw-r--r--libtommath/bn_mp_exptmod_fast.c321
1 files changed, 0 insertions, 321 deletions
diff --git a/libtommath/bn_mp_exptmod_fast.c b/libtommath/bn_mp_exptmod_fast.c
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--- a/libtommath/bn_mp_exptmod_fast.c
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@@ -1,321 +0,0 @@
-#include <tommath_private.h>
-#ifdef BN_MP_EXPTMOD_FAST_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, tstdenis82@gmail.com, http://libtom.org
- */
-
-/* computes Y == G**X mod P, HAC pp.616, Algorithm 14.85
- *
- * Uses a left-to-right k-ary sliding window to compute the modular exponentiation.
- * The value of k changes based on the size of the exponent.
- *
- * Uses Montgomery or Diminished Radix reduction [whichever appropriate]
- */
-
-#ifdef MP_LOW_MEM
- #define TAB_SIZE 32
-#else
- #define TAB_SIZE 256
-#endif
-
-int mp_exptmod_fast (mp_int * G, mp_int * X, mp_int * P, mp_int * Y, int redmode)
-{
- mp_int M[TAB_SIZE], res;
- mp_digit buf, mp;
- int err, bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize;
-
- /* use a pointer to the reduction algorithm. This allows us to use
- * one of many reduction algorithms without modding the guts of
- * the code with if statements everywhere.
- */
- int (*redux)(mp_int*,mp_int*,mp_digit);
-
- /* find window size */
- x = mp_count_bits (X);
- if (x <= 7) {
- winsize = 2;
- } else if (x <= 36) {
- winsize = 3;
- } else if (x <= 140) {
- winsize = 4;
- } else if (x <= 450) {
- winsize = 5;
- } else if (x <= 1303) {
- winsize = 6;
- } else if (x <= 3529) {
- winsize = 7;
- } else {
- winsize = 8;
- }
-
-#ifdef MP_LOW_MEM
- if (winsize > 5) {
- winsize = 5;
- }
-#endif
-
- /* init M array */
- /* init first cell */
- if ((err = mp_init_size(&M[1], P->alloc)) != MP_OKAY) {
- return err;
- }
-
- /* now init the second half of the array */
- for (x = 1<<(winsize-1); x < (1 << winsize); x++) {
- if ((err = mp_init_size(&M[x], P->alloc)) != MP_OKAY) {
- for (y = 1<<(winsize-1); y < x; y++) {
- mp_clear (&M[y]);
- }
- mp_clear(&M[1]);
- return err;
- }
- }
-
- /* determine and setup reduction code */
- if (redmode == 0) {
-#ifdef BN_MP_MONTGOMERY_SETUP_C
- /* now setup montgomery */
- if ((err = mp_montgomery_setup (P, &mp)) != MP_OKAY) {
- goto LBL_M;
- }
-#else
- err = MP_VAL;
- goto LBL_M;
-#endif
-
- /* automatically pick the comba one if available (saves quite a few calls/ifs) */
-#ifdef BN_FAST_MP_MONTGOMERY_REDUCE_C
- if ((((P->used * 2) + 1) < MP_WARRAY) &&
- (P->used < (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) {
- redux = fast_mp_montgomery_reduce;
- } else
-#endif
- {
-#ifdef BN_MP_MONTGOMERY_REDUCE_C
- /* use slower baseline Montgomery method */
- redux = mp_montgomery_reduce;
-#else
- err = MP_VAL;
- goto LBL_M;
-#endif
- }
- } else if (redmode == 1) {
-#if defined(BN_MP_DR_SETUP_C) && defined(BN_MP_DR_REDUCE_C)
- /* setup DR reduction for moduli of the form B**k - b */
- mp_dr_setup(P, &mp);
- redux = mp_dr_reduce;
-#else
- err = MP_VAL;
- goto LBL_M;
-#endif
- } else {
-#if defined(BN_MP_REDUCE_2K_SETUP_C) && defined(BN_MP_REDUCE_2K_C)
- /* setup DR reduction for moduli of the form 2**k - b */
- if ((err = mp_reduce_2k_setup(P, &mp)) != MP_OKAY) {
- goto LBL_M;
- }
- redux = mp_reduce_2k;
-#else
- err = MP_VAL;
- goto LBL_M;
-#endif
- }
-
- /* setup result */
- if ((err = mp_init_size (&res, P->alloc)) != MP_OKAY) {
- goto LBL_M;
- }
-
- /* create M table
- *
-
- *
- * The first half of the table is not computed though accept for M[0] and M[1]
- */
-
- if (redmode == 0) {
-#ifdef BN_MP_MONTGOMERY_CALC_NORMALIZATION_C
- /* now we need R mod m */
- if ((err = mp_montgomery_calc_normalization (&res, P)) != MP_OKAY) {
- goto LBL_RES;
- }
-
- /* now set M[1] to G * R mod m */
- if ((err = mp_mulmod (G, &res, P, &M[1])) != MP_OKAY) {
- goto LBL_RES;
- }
-#else
- err = MP_VAL;
- goto LBL_RES;
-#endif
- } else {
- mp_set(&res, 1);
- if ((err = mp_mod(G, P, &M[1])) != MP_OKAY) {
- goto LBL_RES;
- }
- }
-
- /* compute the value at M[1<<(winsize-1)] by squaring M[1] (winsize-1) times */
- if ((err = mp_copy (&M[1], &M[1 << (winsize - 1)])) != MP_OKAY) {
- goto LBL_RES;
- }
-
- for (x = 0; x < (winsize - 1); x++) {
- if ((err = mp_sqr (&M[1 << (winsize - 1)], &M[1 << (winsize - 1)])) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&M[1 << (winsize - 1)], P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
- }
-
- /* create upper table */
- for (x = (1 << (winsize - 1)) + 1; x < (1 << winsize); x++) {
- if ((err = mp_mul (&M[x - 1], &M[1], &M[x])) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&M[x], P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
- }
-
- /* set initial mode and bit cnt */
- mode = 0;
- bitcnt = 1;
- buf = 0;
- digidx = X->used - 1;
- bitcpy = 0;
- bitbuf = 0;
-
- for (;;) {
- /* grab next digit as required */
- if (--bitcnt == 0) {
- /* if digidx == -1 we are out of digits so break */
- if (digidx == -1) {
- break;
- }
- /* read next digit and reset bitcnt */
- buf = X->dp[digidx--];
- bitcnt = (int)DIGIT_BIT;
- }
-
- /* grab the next msb from the exponent */
- y = (mp_digit)(buf >> (DIGIT_BIT - 1)) & 1;
- buf <<= (mp_digit)1;
-
- /* if the bit is zero and mode == 0 then we ignore it
- * These represent the leading zero bits before the first 1 bit
- * in the exponent. Technically this opt is not required but it
- * does lower the # of trivial squaring/reductions used
- */
- if ((mode == 0) && (y == 0)) {
- continue;
- }
-
- /* if the bit is zero and mode == 1 then we square */
- if ((mode == 1) && (y == 0)) {
- if ((err = mp_sqr (&res, &res)) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&res, P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
- continue;
- }
-
- /* else we add it to the window */
- bitbuf |= (y << (winsize - ++bitcpy));
- mode = 2;
-
- if (bitcpy == winsize) {
- /* ok window is filled so square as required and multiply */
- /* square first */
- for (x = 0; x < winsize; x++) {
- if ((err = mp_sqr (&res, &res)) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&res, P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
- }
-
- /* then multiply */
- if ((err = mp_mul (&res, &M[bitbuf], &res)) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&res, P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
-
- /* empty window and reset */
- bitcpy = 0;
- bitbuf = 0;
- mode = 1;
- }
- }
-
- /* if bits remain then square/multiply */
- if ((mode == 2) && (bitcpy > 0)) {
- /* square then multiply if the bit is set */
- for (x = 0; x < bitcpy; x++) {
- if ((err = mp_sqr (&res, &res)) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&res, P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
-
- /* get next bit of the window */
- bitbuf <<= 1;
- if ((bitbuf & (1 << winsize)) != 0) {
- /* then multiply */
- if ((err = mp_mul (&res, &M[1], &res)) != MP_OKAY) {
- goto LBL_RES;
- }
- if ((err = redux (&res, P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
- }
- }
- }
-
- if (redmode == 0) {
- /* fixup result if Montgomery reduction is used
- * recall that any value in a Montgomery system is
- * actually multiplied by R mod n. So we have
- * to reduce one more time to cancel out the factor
- * of R.
- */
- if ((err = redux(&res, P, mp)) != MP_OKAY) {
- goto LBL_RES;
- }
- }
-
- /* swap res with Y */
- mp_exch (&res, Y);
- err = MP_OKAY;
-LBL_RES:mp_clear (&res);
-LBL_M:
- mp_clear(&M[1]);
- for (x = 1<<(winsize-1); x < (1 << winsize); x++) {
- mp_clear (&M[x]);
- }
- return err;
-}
-#endif
-
-
-/* ref: $Format:%D$ */
-/* git commit: $Format:%H$ */
-/* commit time: $Format:%ai$ */
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