summaryrefslogtreecommitdiffstats
path: root/libtommath/bn_mp_exptmod_fast.c
diff options
context:
space:
mode:
Diffstat (limited to 'libtommath/bn_mp_exptmod_fast.c')
-rw-r--r--libtommath/bn_mp_exptmod_fast.c522
1 files changed, 263 insertions, 259 deletions
diff --git a/libtommath/bn_mp_exptmod_fast.c b/libtommath/bn_mp_exptmod_fast.c
index 2a3b3c9..a9cd742 100644
--- a/libtommath/bn_mp_exptmod_fast.c
+++ b/libtommath/bn_mp_exptmod_fast.c
@@ -24,298 +24,302 @@
*/
#ifdef MP_LOW_MEM
- #define TAB_SIZE 32
+#define TAB_SIZE 32
#else
- #define TAB_SIZE 256
+#define TAB_SIZE 256
#endif
-int mp_exptmod_fast (mp_int * G, mp_int * X, mp_int * P, mp_int * Y, int redmode)
+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;
- }
+ 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;
- }
+ if (winsize > 5) {
+ winsize = 5;
+ }
#endif
- /* init M array */
- /* init first cell */
- if ((err = mp_init(&M[1])) != 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(&M[x])) != 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;
- }
+ /* init M array */
+ /* init first cell */
+ if ((err = mp_init(&M[1])) != 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(&M[x])) != 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;
+ err = MP_VAL;
+ goto LBL_M;
#endif
- /* automatically pick the comba one if available (saves quite a few calls/ifs) */
+ /* 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
+ 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;
+ /* use slower baseline Montgomery method */
+ redux = mp_montgomery_reduce;
#else
- err = MP_VAL;
- goto LBL_M;
+ err = MP_VAL;
+ goto LBL_M;
#endif
- }
- } else if (redmode == 1) {
+ }
+ } 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;
+ /* 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;
+ err = MP_VAL;
+ goto LBL_M;
#endif
- } else {
+ } 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;
+ /* 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;
+ err = MP_VAL;
+ goto LBL_M;
#endif
- }
+ }
- /* setup result */
- if ((err = mp_init (&res)) != MP_OKAY) {
- goto LBL_M;
- }
+ /* setup result */
+ if ((err = mp_init(&res)) != MP_OKAY) {
+ goto LBL_M;
+ }
- /* create M table
- *
+ /* create M table
+ *
- *
- * The first half of the table is not computed though accept for M[0] and M[1]
- */
+ *
+ * The first half of the table is not computed though accept for M[0] and M[1]
+ */
- if (redmode == 0) {
+ 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;
- }
-#else
- err = MP_VAL;
- goto LBL_RES;
+ /* now we need R mod m */
+ if ((err =
+ mp_montgomery_calc_normalization(&res, P)) != MP_OKAY) {
+ goto LBL_RES;
+ }
+#else
+ err = MP_VAL;
+ goto LBL_RES;
#endif
- /* now set M[1] to G * R mod m */
- if ((err = mp_mulmod (G, &res, P, &M[1])) != MP_OKAY) {
- goto LBL_RES;
- }
- } 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);
+ /* now set M[1] to G * R mod m */
+ if ((err = mp_mulmod(G, &res, P, &M[1])) != MP_OKAY) {
+ goto LBL_RES;
+ }
+ } 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;
+ mp_clear(&M[1]);
+ for (x = 1 << (winsize - 1); x < (1 << winsize); x++) {
+ mp_clear(&M[x]);
+ }
+ return err;
}
#endif
-
/* $Source: /cvs/libtom/libtommath/bn_mp_exptmod_fast.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */
generated by cgit (git 2.34.1) at 2024-05-06 01:44:05 +0000