--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/ecc/ltc_ecc_mulmod.c	Thu Feb 22 14:53:49 2007 +0000
@@ -0,0 +1,222 @@
+/* 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, [email protected], 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 $ */