Projective coordinates for prime curves

[u/mdw/catacomb] / exp.h

diff --git a/exp.h b/exp.h
index 6cfdfd8..fc9e3a9 100644 (file)
--- a/exp.h
+++ b/exp.h
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: exp.h,v 1.1 2001/06/16 13:00:59 mdw Exp $
+ * $Id: exp.h,v 1.1.4.1 2004/03/20 00:13:31 mdw Exp $
  *
  * Generalized exponentiation
  *
@@ -30,6 +30,9 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: exp.h,v $
+ * Revision 1.1.4.1  2004/03/20 00:13:31  mdw
+ * Projective coordinates for prime curves
+ *
  * Revision 1.1  2001/06/16 13:00:59  mdw
  * New generic exponentation code.  Includes sliding-window simultaneous
  * exponentiation.
@@ -99,6 +102,10 @@ typedef struct exp_simul {
  * @EXP_MUL(a, x)@             Multiplies @a@ by @x@ (writing the result
  *                             back to @a@).
  *
+ * @EXP_FIX(x)@                        Makes @x@ be a canonical representation of
+ *                             its value.  All multiplications have the
+ *                             right argument canonical.
+ *
  * @EXP_SQR(a)@                        Multiplies @a@ by itself.
  *
  * @EXP_SETMUL(d, x, y)@       Sets @d@ to be the product of @x@ and @y@.
@@ -140,6 +147,7 @@ typedef struct exp_simul {
                                                                        \
   /* --- Do the main body of the work --- */                           \
                                                                        \
+  EXP_FIX(g);                                                          \
   for (;;) {                                                           \
     EXP_MUL(a, g);                                                     \
     sq = 0;                                                            \
@@ -184,11 +192,15 @@ exp_simple_exit:;                                                 \
                                                                        \
   /* --- Do the precomputation --- */                                  \
                                                                        \
+  EXP_FIX(g);                                                          \
   EXP_SETSQR(g2, g);                                                   \
+  EXP_FIX(g2);                                                         \
   v = xmalloc(EXP_TABSZ * sizeof(EXP_TYPE));                           \
   EXP_COPY(v[0], g);                                                   \
-  for (i = 1; i < EXP_TABSZ; i++)                                      \
+  for (i = 1; i < EXP_TABSZ; i++) {                                    \
     EXP_SETMUL(v[i], v[i - 1], g2);                                    \
+    EXP_FIX(v[i]);                                                     \
+  }                                                                    \
   EXP_DROP(g2);                                                                \
                                                                        \
   /* --- Skip top-end zero bits --- *                                  \
@@ -286,17 +298,21 @@ exp_window_exit:;                                                 \
   j = 1;                                                               \
   for (i = 0; i < n; i++) {                                            \
     EXP_COPY(v[j], f[n - 1 - i].base);                                 \
+    EXP_FIX(v[j]);                                                     \
     j <<= 1;                                                           \
   }                                                                    \
   k = n * EXP_WINSZ;                                                   \
   jj = 1;                                                              \
   for (; i < k; i++) {                                                 \
     EXP_SETSQR(v[j], v[jj]);                                           \
+    EXP_FIX(v[j]);                                                     \
     j <<= 1; jj <<= 1;                                                 \
   }                                                                    \
   for (i = 1; i < vn; i <<= 1) {                                       \
-    for (j = 1; j < i; j++)                                            \
+    for (j = 1; j < i; j++) {                                          \
       EXP_SETMUL(v[j + i], v[j], v[i]);                                        \
+      EXP_FIX(v[j + i]);                                               \
+    }                                                                  \
   }                                                                    \
                                                                        \
   /* --- Set up the bitscanners --- *                                  \
@@ -381,7 +397,7 @@ exp_window_exit:;                                                   \
                                                                        \
 exp_simul_done:                                                                \
   while (sq--) EXP_SQR(a);                                             \
-  for (i = 1; i < vn; i++)                                     \
+  for (i = 1; i < vn; i++)                                             \
     EXP_DROP(v[i]);                                                    \
   xfree(v);                                                            \
 } while (0)