ecc: Implement Curve Ed25519 signing and verification.

* cipher/ecc-curves.c (domain_parms): Add curve "Ed25519".
* cipher/ecc.c (reverse_buffer): New.
(eddsa_encodempi): New.
(eddsa_encodepoint): New.
(eddsa_decodepoint): New.
(sign_eddsa): Implement.
(verify_eddsa): Implement.
(ecc_sign): Init unused Q.  Pass public key to sign_eddsa.
(ecc_verify): Init pk.Q if not used.  Pass public key verbatim to
verify_eddsa.
* cipher/pubkey.c (sexp_elements_extract): Add arg OPAQUE.  Change all
callers to pass 0.
(sexp_to_sig): Add arg OPAQUE and pass it to sexp_elements_extract.
(sexp_data_to_mpi): Allow for a zero length "value".
(gcry_pk_verify): Reorder parameter processing.  Pass OPAQUE flag as
required.
* mpi/ec.c (ec_invm): Print a warning if the inverse does not exist.
(_gcry_mpi_ec_get_affine): Implement for our Twisted Edwards curve
model.
(dup_point_twistededwards): Implement.
(add_points_twistededwards): Implement.
(_gcry_mpi_ec_mul_point): Support Twisted Edwards.

* mpi/mpicoder.c (do_get_buffer): Add arg FILL_LE.
(_gcry_mpi_get_buffer): Ditto.  Change all callers.
(_gcry_mpi_get_secure_buffer): Ditto.

* src/sexp.c (_gcry_sexp_nth_opaque_mpi): New.

* tests/t-ed25519.c: New.
* tests/t-ed25519.inp: New.
* tests/t-mpi-point.c (basic_ec_math_simplified): Print some output
only in debug mode.
(twistededwards_math): New test.
(main): Call new test.
--

This is a non optimized version which takes far too long.  On my X220
Thinkpad the 1024 test cases take 14 seconds (12 with --sign-with-pk).
There should be a lot of room for improvements.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/src/mpi.h b/src/mpi.h
index bf731a3b..bd931681 100644
--- a/src/mpi.h
+++ b/src/mpi.h
@@ -159,8 +159,10 @@ gcry_mpi_t _gcry_mpi_const (enum gcry_mpi_constants no);
 /*-- mpicoder.c --*/
 void  _gcry_log_mpidump( const char *text, gcry_mpi_t a );
 u32   _gcry_mpi_get_keyid( gcry_mpi_t a, u32 *keyid );
-byte *_gcry_mpi_get_buffer( gcry_mpi_t a, unsigned *nbytes, int *sign );
-byte *_gcry_mpi_get_secure_buffer( gcry_mpi_t a, unsigned *nbytes, int *sign );
+byte *_gcry_mpi_get_buffer (gcry_mpi_t a, unsigned int fill_le,
+                            unsigned int *r_nbytes, int *sign);
+byte *_gcry_mpi_get_secure_buffer (gcry_mpi_t a, unsigned int fill_le,
+                                   unsigned *r_nbytes, int *sign);
 void  _gcry_mpi_set_buffer ( gcry_mpi_t a, const void *buffer,
                              unsigned int nbytes, int sign );
 
@@ -274,6 +276,7 @@ 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
   {