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, 24 insertions, 0 deletions

diff --git a/src/sexp.c b/src/sexp.c
index 0e96f0b0..d8812c7e 100644
--- a/src/sexp.c
+++ b/src/sexp.c
@@ -783,6 +783,30 @@ gcry_sexp_nth_mpi (gcry_sexp_t list, int number, int mpifmt)
 }
 
 
+/*
+ * Get data from the car and store return it as an opaque MPI.
+ */
+gcry_mpi_t
+_gcry_sexp_nth_opaque_mpi (gcry_sexp_t list, int number)
+{
+  char *p;
+  size_t n;
+  gcry_mpi_t a;
+
+  p = gcry_sexp_nth_buffer (list, number, &n);
+  if (!p)
+    return NULL;
+
+  a = gcry_is_secure (list)? _gcry_mpi_snew (0) : _gcry_mpi_new (0);
+  if (a)
+    gcry_mpi_set_opaque (a, p, n*8);
+  else
+    gcry_free (p);
+
+  return a;
+}
+
+
 /****************
  * Get the CDR
  */