/* -*-c-*-
*
- * $Id: ec.c,v 1.4.4.2 2004/03/20 00:13:31 mdw Exp $
+ * $Id: ec.c,v 1.8 2004/04/01 12:50:09 mdw Exp $
*
* Elliptic curve definitions
*
/*----- Revision history --------------------------------------------------*
*
* $Log: ec.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 2004/03/27 17:54:11 mdw
+ * Standard curves and curve checking.
+ *
+ * Revision 1.6 2004/03/23 15:19:32 mdw
+ * Test elliptic curves more thoroughly.
+ *
+ * Revision 1.5 2004/03/21 22:52:06 mdw
+ * Merge and close elliptic curve branch.
+ *
* Revision 1.4.4.2 2004/03/20 00:13:31 mdw
* Projective coordinates for prime curves
*
/*----- Header files ------------------------------------------------------*/
#include "ec.h"
-#include "ec-exp.h"
/*----- Trivial wrappers --------------------------------------------------*/
+/* --- @ec_samep@ --- *
+ *
+ * Arguments: @ec_curve *c, *d@ = two elliptic curves
+ *
+ * Returns: Nonzero if the curves are identical (not just isomorphic).
+ *
+ * Use: Checks for sameness of curves. This function does the full
+ * check, not just the curve-type-specific check done by the
+ * @sampep@ field operation.
+ */
+
+int ec_samep(ec_curve *c, ec_curve *d)
+{
+ return (field_samep(c->f, d->f) && c->ops == d->ops && EC_SAMEP(c, d));
+}
+
/* --- @ec_create@ --- *
*
* Arguments: @ec *p@ = pointer to an elliptic-curve point
ec *ec_copy(ec *d, const ec *p) { EC_COPY(d, p); return (d); }
+/* --- @ec_eq@ --- *
+ *
+ * Arguments: @const ec *p, *q@ = two points
+ *
+ * Returns: Nonzero if the points are equal. Compares external-format
+ * points.
+ */
+
+int ec_eq(const ec *p, const ec *q) { return (EC_EQ(p, q)); }
+
/*----- Standard curve operations -----------------------------------------*/
+/* --- @ec_stdsamep@ --- *
+ *
+ * Arguments: @ec_curve *c, *d@ = two elliptic curves
+ *
+ * Returns: Nonzero if the curves are identical (not just isomorphic).
+ *
+ * Use: Simple sameness check on @a@ and @b@ curve members.
+ */
+
+int ec_stdsamep(ec_curve *c, ec_curve *d)
+{
+ return (MP_EQ(c->a, d->a) && MP_EQ(c->b, d->b));
+}
+
/* --- @ec_idin@, @ec_idout@, @ec_idfix@ --- *
*
* Arguments: @ec_curve *c@ = pointer to an elliptic curve
ec *ec_sub(ec_curve *c, ec *d, const ec *p, const ec *q)
{
- ec pp, qq;
+ ec pp = EC_INIT, qq = EC_INIT;
EC_IN(c, &pp, p);
EC_IN(c, &qq, q);
- EC_SUB(c, d, &qq, &qq);
+ EC_SUB(c, d, &pp, &qq);
EC_OUT(c, d, d);
EC_DESTROY(&pp);
EC_DESTROY(&qq);
return (rc);
}
-/* --- @ec_imul@, @ec_mul@ --- *
+/* --- @ec_rand@ --- *
*
* Arguments: @ec_curve *c@ = pointer to an elliptic curve
* @ec *d@ = pointer to the destination point
- * @const ec *p@ = pointer to the generator point
- * @mp *n@ = integer multiplier
+ * @grand *r@ = random number source
*
* Returns: The destination @d@.
*
- * Use: Multiplies a point by a scalar, returning %$n p$%. The
- * @imul@ variant uses internal representations for argument
- * and result.
+ * Use: Finds a random point on the given curve.
*/
-ec *ec_imul(ec_curve *c, ec *d, const ec *p, mp *n)
-{
- ec t = EC_INIT;
-
- EC_COPY(&t, p);
- if (t.x && (n->f & MP_BURN))
- t.x->f |= MP_BURN;
- MP_SHRINK(n);
- EC_SETINF(d);
- if (MP_LEN(n) == 0)
- ;
- else {
- if (n->f & MP_NEG)
- EC_NEG(c, &t, &t);
- if (MP_LEN(n) < EXP_THRESH)
- EXP_SIMPLE(*d, t, n);
- else
- EXP_WINDOW(*d, t, n);
- }
- EC_DESTROY(&t);
- return (d);
-}
-
-ec *ec_mul(ec_curve *c, ec *d, const ec *p, mp *n)
+ec *ec_rand(ec_curve *c, ec *d, grand *r)
{
- EC_IN(c, d, p);
- ec_imul(c, d, d, n);
- return (EC_OUT(c, d, d));
+ mp *x = MP_NEW;
+ do x = F_RAND(c->f, x, r); while (!EC_FIND(c, d, x));
+ mp_drop(x);
+ if (grand_range(r, 2)) EC_NEG(c, d, d);
+ return (EC_OUT(c, d, d));
}
/*----- That's all, folks -------------------------------------------------*/