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-rw-r--r--src/pk/ecc/ltc_ecc_mulmod.c222
1 files changed, 222 insertions, 0 deletions
diff --git a/src/pk/ecc/ltc_ecc_mulmod.c b/src/pk/ecc/ltc_ecc_mulmod.c
new file mode 100644
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+++ b/src/pk/ecc/ltc_ecc_mulmod.c
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+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
+ */
+
+/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
+ *
+ * All curves taken from NIST recommendation paper of July 1999
+ * Available at http://csrc.nist.gov/cryptval/dss.htm
+ */
+#include "tomcrypt.h"
+
+/**
+ @file ltc_ecc_mulmod.c
+ ECC Crypto, Tom St Denis
+*/
+
+#ifdef MECC
+#ifndef LTC_ECC_TIMING_RESISTANT
+
+/* size of sliding window, don't change this! */
+#define WINSIZE 4
+
+/**
+ Perform a point multiplication
+ @param k The scalar to multiply by
+ @param G The base point
+ @param R [out] Destination for kG
+ @param modulus The modulus of the field the ECC curve is in
+ @param map Boolean whether to map back to affine or not (1==map, 0 == leave in projective)
+ @return CRYPT_OK on success
+*/
+int ltc_ecc_mulmod(void *k, ecc_point *G, ecc_point *R, void *modulus, int map)
+{
+ ecc_point *tG, *M[8];
+ int i, j, err;
+ void *mu, *mp;
+ unsigned long buf;
+ int first, bitbuf, bitcpy, bitcnt, mode, digidx;
+
+ LTC_ARGCHK(k != NULL);
+ LTC_ARGCHK(G != NULL);
+ LTC_ARGCHK(R != NULL);
+ LTC_ARGCHK(modulus != NULL);
+
+ /* init montgomery reduction */
+ if ((err = mp_montgomery_setup(modulus, &mp)) != CRYPT_OK) {
+ return err;
+ }
+ if ((err = mp_init(&mu)) != CRYPT_OK) {
+ mp_montgomery_free(mp);
+ return err;
+ }
+ if ((err = mp_montgomery_normalization(mu, modulus)) != CRYPT_OK) {
+ mp_montgomery_free(mp);
+ mp_clear(mu);
+ return err;
+ }
+
+ /* alloc ram for window temps */
+ for (i = 0; i < 8; i++) {
+ M[i] = ltc_ecc_new_point();
+ if (M[i] == NULL) {
+ for (j = 0; j < i; j++) {
+ ltc_ecc_del_point(M[j]);
+ }
+ mp_montgomery_free(mp);
+ mp_clear(mu);
+ return CRYPT_MEM;
+ }
+ }
+
+ /* make a copy of G incase R==G */
+ tG = ltc_ecc_new_point();
+ if (tG == NULL) { err = CRYPT_MEM; goto done; }
+
+ /* tG = G and convert to montgomery */
+ if (mp_cmp_d(mu, 1) == LTC_MP_EQ) {
+ if ((err = mp_copy(G->x, tG->x)) != CRYPT_OK) { goto done; }
+ if ((err = mp_copy(G->y, tG->y)) != CRYPT_OK) { goto done; }
+ if ((err = mp_copy(G->z, tG->z)) != CRYPT_OK) { goto done; }
+ } else {
+ if ((err = mp_mulmod(G->x, mu, modulus, tG->x)) != CRYPT_OK) { goto done; }
+ if ((err = mp_mulmod(G->y, mu, modulus, tG->y)) != CRYPT_OK) { goto done; }
+ if ((err = mp_mulmod(G->z, mu, modulus, tG->z)) != CRYPT_OK) { goto done; }
+ }
+ mp_clear(mu);
+ mu = NULL;
+
+ /* calc the M tab, which holds kG for k==8..15 */
+ /* M[0] == 8G */
+ if ((err = ltc_mp.ecc_ptdbl(tG, M[0], modulus, mp)) != CRYPT_OK) { goto done; }
+ if ((err = ltc_mp.ecc_ptdbl(M[0], M[0], modulus, mp)) != CRYPT_OK) { goto done; }
+ if ((err = ltc_mp.ecc_ptdbl(M[0], M[0], modulus, mp)) != CRYPT_OK) { goto done; }
+
+ /* now find (8+k)G for k=1..7 */
+ for (j = 9; j < 16; j++) {
+ if ((err = ltc_mp.ecc_ptadd(M[j-9], tG, M[j-8], modulus, mp)) != CRYPT_OK) { goto done; }
+ }
+
+ /* setup sliding window */
+ mode = 0;
+ bitcnt = 1;
+ buf = 0;
+ digidx = mp_get_digit_count(k) - 1;
+ bitcpy = bitbuf = 0;
+ first = 1;
+
+ /* perform ops */
+ for (;;) {
+ /* grab next digit as required */
+ if (--bitcnt == 0) {
+ if (digidx == -1) {
+ break;
+ }
+ buf = mp_get_digit(k, digidx);
+ bitcnt = (int) ltc_mp.bits_per_digit;
+ --digidx;
+ }
+
+ /* grab the next msb from the ltiplicand */
+ i = (buf >> (ltc_mp.bits_per_digit - 1)) & 1;
+ buf <<= 1;
+
+ /* skip leading zero bits */
+ if (mode == 0 && i == 0) {
+ continue;
+ }
+
+ /* if the bit is zero and mode == 1 then we double */
+ if (mode == 1 && i == 0) {
+ if ((err = ltc_mp.ecc_ptdbl(R, R, modulus, mp)) != CRYPT_OK) { goto done; }
+ continue;
+ }
+
+ /* else we add it to the window */
+ bitbuf |= (i << (WINSIZE - ++bitcpy));
+ mode = 2;
+
+ if (bitcpy == WINSIZE) {
+ /* if this is the first window we do a simple copy */
+ if (first == 1) {
+ /* R = kG [k = first window] */
+ if ((err = mp_copy(M[bitbuf-8]->x, R->x)) != CRYPT_OK) { goto done; }
+ if ((err = mp_copy(M[bitbuf-8]->y, R->y)) != CRYPT_OK) { goto done; }
+ if ((err = mp_copy(M[bitbuf-8]->z, R->z)) != CRYPT_OK) { goto done; }
+ first = 0;
+ } else {
+ /* normal window */
+ /* ok window is filled so double as required and add */
+ /* double first */
+ for (j = 0; j < WINSIZE; j++) {
+ if ((err = ltc_mp.ecc_ptdbl(R, R, modulus, mp)) != CRYPT_OK) { goto done; }
+ }
+
+ /* then add, bitbuf will be 8..15 [8..2^WINSIZE] guaranteed */
+ if ((err = ltc_mp.ecc_ptadd(R, M[bitbuf-8], R, modulus, mp)) != CRYPT_OK) { goto done; }
+ }
+ /* empty window and reset */
+ bitcpy = bitbuf = 0;
+ mode = 1;
+ }
+ }
+
+ /* if bits remain then double/add */
+ if (mode == 2 && bitcpy > 0) {
+ /* double then add */
+ for (j = 0; j < bitcpy; j++) {
+ /* only double if we have had at least one add first */
+ if (first == 0) {
+ if ((err = ltc_mp.ecc_ptdbl(R, R, modulus, mp)) != CRYPT_OK) { goto done; }
+ }
+
+ bitbuf <<= 1;
+ if ((bitbuf & (1 << WINSIZE)) != 0) {
+ if (first == 1){
+ /* first add, so copy */
+ if ((err = mp_copy(tG->x, R->x)) != CRYPT_OK) { goto done; }
+ if ((err = mp_copy(tG->y, R->y)) != CRYPT_OK) { goto done; }
+ if ((err = mp_copy(tG->z, R->z)) != CRYPT_OK) { goto done; }
+ first = 0;
+ } else {
+ /* then add */
+ if ((err = ltc_mp.ecc_ptadd(R, tG, R, modulus, mp)) != CRYPT_OK) { goto done; }
+ }
+ }
+ }
+ }
+
+ /* map R back from projective space */
+ if (map) {
+ err = ltc_ecc_map(R, modulus, mp);
+ } else {
+ err = CRYPT_OK;
+ }
+done:
+ if (mu != NULL) {
+ mp_clear(mu);
+ }
+ mp_montgomery_free(mp);
+ ltc_ecc_del_point(tG);
+ for (i = 0; i < 8; i++) {
+ ltc_ecc_del_point(M[i]);
+ }
+ return err;
+}
+
+#endif
+
+#undef WINSIZE
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_mulmod.c,v $ */
+/* $Revision: 1.24 $ */
+/* $Date: 2006/12/04 05:07:59 $ */
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