X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/79a340293970d5f9b9c000f82769179f9ba551bd..898a4e2555438ff8adb08b4d82690d08715e1048:/mpmont-mexp.c

diff --git a/mpmont-mexp.c b/mpmont-mexp.c
index 1d1266f..7589990 100644
--- a/mpmont-mexp.c
+++ b/mpmont-mexp.c
@@ -1,8 +1,8 @@
 /* -*-c-*-
  *
- * $Id: mpmont-mexp.c,v 1.2 1999/11/21 11:35:10 mdw Exp $
+ * $Id: mpmont-mexp.c,v 1.8 2004/04/01 12:50:09 mdw Exp $
  *
- * Multiplle simultaneous exponentiations
+ * Multiple simultaneous exponentiations
  *
  * (c) 1999 Straylight/Edgeware
  */
@@ -30,6 +30,30 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpmont-mexp.c,v $
+ * Revision 1.8  2004/04/01 12:50:09  mdw
+ * Add cyclic group abstraction, with test code.  Separate off exponentation
+ * functions for better static linking.  Fix a buttload of bugs on the way.
+ * Generally ensure that negative exponents do inversion correctly.  Add
+ * table of standard prime-field subgroups.  (Binary field subgroups are
+ * currently unimplemented but easy to add if anyone ever finds a good one.)
+ *
+ * Revision 1.7  2002/01/13 13:49:14  mdw
+ * Make @const@-correct.
+ *
+ * Revision 1.6  2001/06/16 13:00:20  mdw
+ * Use the generic exponentiation functions.
+ *
+ * Revision 1.5  2000/10/08 12:11:22  mdw
+ * Use @MP_EQ@ instead of @MP_CMP@.
+ *
+ * Revision 1.4  2000/06/17 11:45:09  mdw
+ * Major memory management overhaul.  Added arena support.  Use the secure
+ * arena for secret integers.  Replace and improve the MP management macros
+ * (e.g., replace MP_MODIFY by MP_DEST).
+ *
+ * Revision 1.3  1999/12/10 23:18:39  mdw
+ * Change interface for suggested destinations.
+ *
  * Revision 1.2  1999/11/21 11:35:10  mdw
  * Performance improvement: use @mp_sqr@ and @mpmont_reduce@ instead of
  * @mpmont_mul@ for squaring in exponentiation.
@@ -44,155 +68,72 @@
 #include "mp.h"
 #include "mpmont.h"
 
+#define EXP_WINSZ 3
+#include "mpmont-exp.h"
+
 /*----- Main code ---------------------------------------------------------*/
 
 /* --- @mpmont_mexpr@ --- *
  *
  * Arguments:	@mpmont *mm@ = pointer to Montgomery reduction context
- *		@mpmont_factor *f@ = pointer to array of factors
+ *		@mp *d@ = fake destination
+ *		@const mp_expfactor *f@ = pointer to array of factors
  *		@size_t n@ = number of factors supplied
  *
  * Returns:	If the bases are %$g_0, g_1, \ldots, g_{n-1}$% and the
  *		exponents are %$e_0, e_1, \ldots, e_{n-1}$% then the result
  *		is:
  *
- *		%$g_0^{e_0} g_1^{e_1} \ldots g_{n-1}^{e_{n-1}} R \bmod m$%
+ *		%$g_0^{e_0} g_1^{e_1} \ldots g_{n-1}^{e_{n-1}} \bmod m$%
+ *
+ *		except that the %$g_i$% and result are in Montgomery form.
  */
 
-typedef struct scan {
-  size_t len;
-  mpw w;
-} scan;
-
-mp *mpmont_mexpr(mpmont *mm, mpmont_factor *f, size_t n)
+static mp *mexpr(mpmont *mm, mp *d, mp_expfactor *f, size_t n)
 {
-  size_t vn = 1 << n;
-  mp **v = xmalloc(vn * sizeof(mp *));
-  scan *s;
-  size_t o;
-  unsigned b;
   mp *a = MP_COPY(mm->r);
   mp *spare = MP_NEW;
+  mp *g = MP_NEW;
+  size_t i;
 
-  /* --- Perform the precomputation --- */
-
-  {
-    size_t i, j;
-    size_t mask;
-
-    /* --- Fill in the rest of the array --- *
-     *
-     * Zero never gets used.
-     */
-
-    j = 0;
-    mask = 0;
-    for (i = 1; i < vn; i++) {
-
-      /* --- Check for a new bit entering --- *
-       *
-       * If a bit gets set that wasn't set before, then all the lower bits
-       * are zeroes and I've got to introduce a new base into the array.
-       */
-
-      if ((i & mask) == 0) {
-	v[i] = mpmont_mul(mm, MP_NEW, f[j++].base, mm->r2);
-	mask = i;
-      }
-
-      /* --- Otherwise I can get away with a single multiplication --- *
-       *
-       * In particular, if %$i$% has more than one bit set, then I only need
-       * to calculate %$v_i = v_{\mathit{mask}} v_{i - \mathit{mask}}$%.
-       * Since both are less than %$i$%, they must have already been
-       * computed.
-       */
-
-      else
-	v[i] = mpmont_mul(mm, MP_NEW, v[mask], v[i & ~mask]);
-    }
-  }
-
-  /* --- Set up the bitscanners --- *
-   *
-   * I must scan the exponents from left to right, which is a shame.  It
-   * means that I can't use the standard @mpscan@ stuff, in particular.
-   */
-
-  {
-    size_t i;
-
-    s = xmalloc(n * sizeof(scan));
-    o = 0;
-    for (i = 0; i < n; i++) {
-      s[i].len = MP_LEN(f[i].exp);
-      if (s[i].len > o)
-	o = s[i].len;
-    }
-    b = 0;
-  }
-
-  /* --- Now do the actual calculation --- */
-
-  b = 0;
-  for (;;) {
-    size_t i;
-    size_t j;
-    mp *dd;
-
-    /* --- If no more bits, get some more --- */
-
-    if (!b) {
-      if (!o)
-	break;
-      o--;
-      b = MPW_BITS;
-    }
-
-    /* --- Work out the next index --- */
-
-    j = 0;
-    b--;
-    for (i = 0; i < n; i++) {
-      if (o < s[i].len)
-	j |= (((f[i].exp->v[o] >> b) & 1) << i);
-    }
-
-    /* --- Accumulate the result --- */
-
-    if (spare) {
-      dd = mp_sqr(spare, a);
-      dd = mpmont_reduce(mm, dd, dd);
-      spare = a;
-      a = dd;
-    }
-    
-    if (j) {
-      dd = mpmont_mul(mm, spare, a, v[j]);
-      spare = a;
-      a = dd;
+  for (i = 0; i < n; i++) {
+    mp *t;
+    if (f[i].exp->f & MP_BURN)
+      spare = MP_NEWSEC;
+    if (f[i].exp->f & MP_NEG) {
+      t = mpmont_reduce(mm, f[i].base, f[i].base);
+      mp_gcd(&g, 0, &t, mm->m, t);
+      assert(MP_EQ(g, MP_ONE));
+      f[i].base = mpmont_mul(mm, t, t, mm->r2);
     }
   }
+  mp_drop(g);
+  EXP_SIMUL(a, f, n);
+  mp_drop(d);
+  mp_drop(spare);
+  for (i = 0; i < n; i++)
+    MP_DROP(f[i].base);
+  xfree(f);
+  return (a);
+}
 
-  /* --- Tidy up afterwards --- */
+mp *mpmont_mexpr(mpmont *mm, mp *d, const mp_expfactor *f, size_t n)
+{
+  mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
+  size_t i;
 
-  {
-    size_t i;
-    for (i = 1; i < vn; i++)
-      MP_DROP(v[i]);
-    if (spare)
-      MP_DROP(spare);
-    free(v);
-    free(s);
+  for (i = 0; i < n; i++) {
+    ff[i].base = MP_COPY(f[i].base);
+    ff[i].exp = f[i].exp;
   }
-
-  return (a);
+  return (mexpr(mm, d, ff, n));
 }
 
 /* --- @mpmont_mexp@ --- *
  *
  * Arguments:	@mpmont *mm@ = pointer to Montgomery reduction context
- *		@mpmont_factor *f@ = pointer to array of factors
+ *		@mp *d@ = fake destination
+ *		@const mp_expfactor *f@ = pointer to array of factors
  *		@size_t n@ = number of factors supplied
  *
  * Returns:	Product of bases raised to exponents, all mod @m@.
@@ -200,11 +141,17 @@ mp *mpmont_mexpr(mpmont *mm, mpmont_factor *f, size_t n)
  * Use:		Convenient interface over @mpmont_mexpr@.
  */
 
-mp *mpmont_mexp(mpmont *mm, mpmont_factor *f, size_t n)
+mp *mpmont_mexp(mpmont *mm, mp *d, const mp_expfactor *f, size_t n)
 {
-  mp *d = mpmont_mexpr(mm, f, n);
-  d = mpmont_reduce(mm, d, d);
-  return (d);
+  mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
+  size_t i;
+
+  for (i = 0; i < n; i++) {
+    ff[i].base = mpmont_mul(mm, MP_NEW, f[i].base, mm->r2);
+    ff[i].exp = f[i].exp;
+  }
+  d = mexpr(mm, d, ff, n);
+  return (mpmont_reduce(mm, d, d));
 }
 
 /*----- Test rig ----------------------------------------------------------*/
@@ -216,7 +163,7 @@ mp *mpmont_mexp(mpmont *mm, mpmont_factor *f, size_t n)
 static int verify(size_t n, dstr *v)
 {
   mp *m = *(mp **)v[0].buf;
-  mpmont_factor *f = xmalloc(n * sizeof(*f));
+  mp_expfactor *f = xmalloc(n * sizeof(*f));
   mp *r, *rr;
   size_t i, j;
   mpmont mm;
@@ -230,8 +177,8 @@ static int verify(size_t n, dstr *v)
 
   rr = *(mp **)v[j].buf;
   mpmont_create(&mm, m);
-  r = mpmont_mexp(&mm, f, n);
-  if (MP_CMP(r, !=, rr)) {
+  r = mpmont_mexp(&mm, MP_NEW, f, n);
+  if (!MP_EQ(r, rr)) {
     fputs("\n*** mexp failed\n", stderr);
     fputs("m = ", stderr); mp_writefile(m, stderr, 10);
     for (i = 0; i < n; i++) {
@@ -254,6 +201,7 @@ static int verify(size_t n, dstr *v)
   MP_DROP(r);
   MP_DROP(rr);
   mpmont_destroy(&mm);
+  assert(mparena_count(MPARENA_GLOBAL) == 0);
   return (ok);
 }