X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/4640a0dd947f422cfda780c62da342792af27b7b..c65df27983057ec76ed0e72bb370f9a5ae7dad28:/mpmont.c

diff --git a/mpmont.c b/mpmont.c
index 2371de8..39f51ed 100644
--- a/mpmont.c
+++ b/mpmont.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpmont.c,v 1.15 2001/06/16 13:00:20 mdw Exp $
+ * $Id: mpmont.c,v 1.19 2004/04/08 01:36:15 mdw Exp $
  *
  * Montgomery reduction
  *
@@ -27,71 +27,10 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: mpmont.c,v $
- * Revision 1.15  2001/06/16 13:00:20  mdw
- * Use the generic exponentiation functions.
- *
- * Revision 1.14  2001/02/22 09:04:26  mdw
- * Cosmetic fix.
- *
- * Revision 1.13  2001/02/03 12:00:29  mdw
- * Now @mp_drop@ checks its argument is non-NULL before attempting to free
- * it.  Note that the macro version @MP_DROP@ doesn't do this.
- *
- * Revision 1.12  2000/10/08 15:48:35  mdw
- * Rename Karatsuba constants now that we have @gfx_kmul@ too.
- *
- * Revision 1.11  2000/10/08 12:04:27  mdw
- * (mpmont_reduce, mpmont_mul): Cope with negative numbers.
- *
- * Revision 1.10  2000/07/29 17:05:43  mdw
- * (mpmont_expr): Use sliding window exponentiation, with a drop-through
- * for small exponents to use a simple left-to-right bitwise routine.  This
- * can reduce modexp times by up to a quarter.
- *
- * Revision 1.9  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 1.8  1999/12/22 15:55:00  mdw
- * Adjust Karatsuba parameters.
- *
- * Revision 1.7  1999/12/11 01:51:14  mdw
- * Use a Karatsuba-based reduction for large moduli.
- *
- * Revision 1.6  1999/12/10 23:18:39  mdw
- * Change interface for suggested destinations.
- *
- * Revision 1.5  1999/11/22 13:58:40  mdw
- * Add an option to disable Montgomery reduction, so that performance
- * comparisons can be done.
- *
- * Revision 1.4  1999/11/21 12:27:06  mdw
- * Remove a division from the Montgomery setup by calculating
- * %$R^2 \bmod m$% first and then %$R \bmod m$% by Montgomery reduction of
- * %$R^2$%.
- *
- * Revision 1.3  1999/11/21 11:35:10  mdw
- * Performance improvement: use @mp_sqr@ and @mpmont_reduce@ instead of
- * @mpmont_mul@ for squaring in exponentiation.
- *
- * Revision 1.2  1999/11/19 13:17:26  mdw
- * Add extra interface to exponentiation which returns a Montgomerized
- * result.
- *
- * Revision 1.1  1999/11/17 18:02:16  mdw
- * New multiprecision integer arithmetic suite.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "mp.h"
 #include "mpmont.h"
-#include "mpmont-exp.h"
 
 /*----- Tweakables --------------------------------------------------------*/
 
@@ -135,15 +74,9 @@ void mpmont_create(mpmont *mm, mp *m)
   mp *r2 = mp_new(2 * n + 1, 0);
   mp r;
 
-  /* --- Validate the arguments --- */
-
-  assert(((void)"Montgomery modulus must be positive",
-	  (m->f & MP_NEG) == 0));
-  assert(((void)"Montgomery modulus must be odd", m->v[0] & 1));
-
   /* --- Take a copy of the modulus --- */
 
-  mp_shrink(m);
+  assert(MP_ISPOS(m) && MP_ISODD(m));
   mm->m = MP_COPY(m);
 
   /* --- Determine %$R^2$% --- */
@@ -155,8 +88,7 @@ void mpmont_create(mpmont *mm, mp *m)
   /* --- Find the magic value @mi@ --- */
 
   mp_build(&r, r2->v + n, r2->vl);
-  mm->mi = MP_NEW;
-  mp_gcd(0, 0, &mm->mi, &r, m);
+  mm->mi = mp_modinv(MP_NEW, m, &r);
   mm->mi = mp_sub(mm->mi, &r, mm->mi);
 
   /* --- Discover the values %$R \bmod m$% and %$R^2 \bmod m$% --- */
@@ -367,53 +299,6 @@ mp *mpmont_mul(mpmont *mm, mp *d, mp *a, mp *b)
 
 #endif
 
-/*----- Exponentiation ----------------------------------------------------*/
-
-/* --- @mpmont_expr@ --- *
- *
- * Arguments:	@mpmont *mm@ = pointer to Montgomery reduction context
- *		@mp *d@ = fake destination
- *		@mp *a@ = base
- *		@mp *e@ = exponent
- *
- * Returns:	Result, %$(a R^{-1})^e R \bmod m$%.
- */
-
-mp *mpmont_expr(mpmont *mm, mp *d, mp *a, mp *e)
-{
-  mp *x = MP_COPY(mm->r);
-  mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
-
-  MP_SHRINK(e);
-  if (MP_LEN(e) == 0)
-    ;
-  else if (MP_LEN(e) < EXP_THRESH)
-    EXP_SIMPLE(x, a, e);
-  else
-    EXP_WINDOW(x, a, e);
-  mp_drop(d);
-  mp_drop(spare);
-  return (x);
-}
-
-/* --- @mpmont_exp@ --- *
- *
- * Arguments:	@mpmont *mm@ = pointer to Montgomery reduction context
- *		@mp *d@ = fake destination
- *		@mp *a@ = base
- *		@mp *e@ = exponent
- *
- * Returns:	Result, %$a^e \bmod m$%.
- */
-
-mp *mpmont_exp(mpmont *mm, mp *d, mp *a, mp *e)
-{
-  d = mpmont_mul(mm, d, a, mm->r2);
-  d = mpmont_expr(mm, d, d, e);
-  d = mpmont_reduce(mm, d, d);
-  return (d);
-}
-
 /*----- Test rig ----------------------------------------------------------*/
 
 #ifdef TEST_RIG
@@ -523,46 +408,9 @@ static int tmul(dstr *v)
   return ok;
 }
 
-static int texp(dstr *v)
-{
-  mp *m = *(mp **)v[0].buf;
-  mp *a = *(mp **)v[1].buf;
-  mp *b = *(mp **)v[2].buf;
-  mp *r = *(mp **)v[3].buf;
-  mp *mr;
-  int ok = 1;
-
-  mpmont mm;
-  mpmont_create(&mm, m);
-
-  mr = mpmont_exp(&mm, MP_NEW, a, b);
-
-  if (!MP_EQ(mr, r)) {
-    fputs("\n*** montgomery modexp failed", stderr);
-    fputs("\n m = ", stderr); mp_writefile(m, stderr, 10);
-    fputs("\n a = ", stderr); mp_writefile(a, stderr, 10);
-    fputs("\n e = ", stderr); mp_writefile(b, stderr, 10);
-    fputs("\n r = ", stderr); mp_writefile(r, stderr, 10);
-    fputs("\nmr = ", stderr); mp_writefile(mr, stderr, 10);
-    fputc('\n', stderr);
-    ok = 0;
-  }
-
-  MP_DROP(m);
-  MP_DROP(a);
-  MP_DROP(b);
-  MP_DROP(r);
-  MP_DROP(mr);
-  mpmont_destroy(&mm);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return ok;
-}
-
-
 static test_chunk tests[] = {
   { "create", tcreate, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
   { "mul", tmul, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
-  { "exp", texp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
   { 0, 0, { 0 } },
 };