X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/7c0acba656af3823577d1341f39c0bbe86632681..a2a74efe4b1276b1efec12f25fd65f0df060f38a:/calc/ecp.cal

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+/* -*-apcalc-*-
+ *
+ * $Id: ecp.cal,v 1.1 2000/10/08 16:01:37 mdw Exp $
+ *
+ * Testbed for elliptic curve arithmetic over prime fields
+ *
+ * (c) 2000 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: ecp.cal,v $
+ * Revision 1.1  2000/10/08 16:01:37  mdw
+ * Prototypes of various bits of code.
+ *
+ */
+
+/*----- Object types ------------------------------------------------------*/
+
+obj ecp_curve { a, b, p };
+obj ecp_pt { x, y, e };
+
+/*----- Main code ---------------------------------------------------------*/
+
+define ecp_curve(a, b, p)
+{
+  local obj ecp_curve e;
+  e.a = a;
+  e.b = b;
+  e.p = p;
+  return (e);
+}
+
+define ecp_pt(x, y, e)
+{
+  local obj ecp_pt p;
+  p.x = x % e.p;
+  p.y = y % e.p;
+  p.e = e;
+  return (p);
+}
+
+define ecp_pt_print(a)
+{
+  print "(" : a.x : ", " : a.y : ")" :;
+}
+
+define ecp_pt_add(a, b)
+{
+  local e, alpha;
+  local obj ecp_pt d;
+
+  if (a == 0)
+    d = b;
+  else if (b == 0)
+    d = a;
+  else if (!istype(a, b))
+    quit "bad type arguments to ecp_pt_add";
+  else if (a.e != b.e)
+    quit "points from different curves in ecp_pt_add";
+  else {
+    e = a.e;
+    if (a.x == b.x) {
+      if (a.y != b.y) {
+        return (0);
+      }
+      alpha = (3 * a.x^2 + e.a) * minv(2 * a.y, e.p) % e.p;
+    } else
+      alpha = (b.y - a.y) * minv(b.x - a.x, e.p) % e.p;
+
+    d.x = (alpha^2 - a.x - b.x) % e.p;
+    d.y = (-a.y + alpha * (a.x - d.x)) % e.p;
+    d.e = e;
+  }
+
+  return (d);
+}
+
+define ecp_pt_neg(a)
+{
+  local obj ecp_pt d;
+  d.x = a.x;
+  d.y = -a.y;
+  d.e = a.e;
+  return (d);
+}
+
+define ecp_pt_mul(a, b)
+{
+  local p, n;
+  local d;
+
+  if (istype(a, 1)) {
+    n = a;
+    p = b;
+  } else if (istype(b, 1)) {
+    n = b;
+    p = a;
+  } else
+    return (newerror("bad arguments to ecp_pt_mul"));
+
+  d = 0;
+  while (n) {
+    if (n & 1)
+      d += p;
+    n >>= 1;
+    p += p;
+  }
+  return (d);
+}
+
+/*----- That's all, folks -------------------------------------------------*/
+