Curve25519 support.

* agent/cvt-openpgp.c (get_keygrip): Handle Curve25519.
(convert_secret_key, convert_transfer_key): Ditto.
* common/openpgp-oid.c (oidtable): Add Curve25519.
(oid_crv25519, openpgp_oid_is_crv25519): New.
* common/util.h (openpgp_oid_is_crv25519): New.
* g10/ecdh.c (pk_ecdh_encrypt_with_shared_point): Handle the case
with Montgomery curve which uses x-only coordinate.
* g10/keygen.c (gen_ecc): Handle Curve25519.
(ask_curve): Change the API and second arg is to return subkey algo.
(generate_keypair, generate_subkeypair): Follow chage of ask_curve.
* g10/keyid.c (keygrip_from_pk): Handle Curve25519.
* g10/pkglue.c (pk_encrypt): Handle Curve25519.
* g10/pubkey-enc.c (get_it): Handle the case with Montgomery curve.
* scd/app-openpgp.c (ECC_FLAG_DJB_TWEAK): New.
(send_key_attr): Work with general ECC, Ed25519, and Curve25519.
(get_public_key): Likewise.
(ecc_writekey): Handle flag_djb_tweak.

--

When libgcrypt has Curve25519, GnuPG now supports Curve25519.

1 files changed, 5 insertions, 1 deletions

diff --git a/g10/pkglue.c b/g10/pkglue.c
index d72275b81..a83462187 100644
--- a/g10/pkglue.c
+++ b/g10/pkglue.c
@@ -228,9 +228,13 @@ pk_encrypt (pubkey_algo_t algo, gcry_mpi_t *resarr, gcry_mpi_t data,
             rc = gpg_error_from_syserror ();
           else
             {
+              int with_djb_tweak_flag = openpgp_oid_is_crv25519 (pkey[0]);
+
               /* Now use the ephemeral secret to compute the shared point.  */
               rc = gcry_sexp_build (&s_pkey, NULL,
-                                    "(public-key(ecdh(curve%s)(q%m)))",
+                                    with_djb_tweak_flag ?
+                                    "(public-key(ecdh(curve%s)(flags djb-tweak)(q%m)))"
+                                    : "(public-key(ecdh(curve%s)(q%m)))",
                                     curve, pkey[1]);
               xfree (curve);
               /* Put K into a simplified S-expression.  */