Prepare support for non-Weierstrass EC equations.

* src/mpi.h (gcry_mpi_ec_models): New.
* src/ec-context.h (mpi_ec_ctx_s): Add MODEL.
* cipher/ecc-common.h (elliptic_curve_t): Ditto.
* cipher/ecc-curves.c (ecc_domain_parms_t): Ditto.
(domain_parms): Mark als as Weierstrass.
(_gcry_ecc_fill_in_curve): Check model.
(_gcry_ecc_get_curve): Set model to Weierstrass.
* cipher/ecc-misc.c (_gcry_ecc_model2str): New.
* cipher/ecc.c (generate_key, ecc_generate_ext): Print model in the
debug output.

* mpi/ec.c (_gcry_mpi_ec_dup_point): Switch depending on model.
Factor code out to ...
(dup_point_weierstrass): new.
(dup_point_montgomery, dup_point_twistededwards): New stub functions.
(_gcry_mpi_ec_add_points): Switch depending on model.  Factor code out
to ...
(add_points_weierstrass): new.
(add_points_montgomery, add_points_twistededwards): New stub
functions.

* tests/Makefile.am (TESTS): Reorder tests.

Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/mpi.h b/src/mpi.h
index fd265bf2..0114dba7 100644
--- a/src/mpi.h
+++ b/src/mpi.h
@@ -272,6 +272,18 @@ void _gcry_mpi_get_point (gcry_mpi_t x, gcry_mpi_t y, gcry_mpi_t z,
 void _gcry_mpi_snatch_point (gcry_mpi_t x, gcry_mpi_t y, gcry_mpi_t z,
                              mpi_point_t point);
 
+/* Models describing an elliptic curve.  */
+enum gcry_mpi_ec_models
+  {
+
+    MPI_EC_WEIERSTRASS = 0,
+    MPI_EC_MONTGOMERY,
+    MPI_EC_TWISTEDEDWARDS
+    /* The equation for Twisted Edwards curves is
+          ax^2 + y^2 = 1 + bx^2y^2
+       Note that we use 'b' instead of the commonly used 'd'.  */
+  };
+
 /* Context used with elliptic curve functions.  */
 struct mpi_ec_ctx_s;
 typedef struct mpi_ec_ctx_s *mpi_ec_t;