We need a helper function in GPGM to extract the PGP ECC parameters from a key. These are required by Kleopatra to be passed to the KEYTOCARD command.
We need something similar to this:
char *
ecdh_param_str_from_pk (PKT_public_key *pk)
{
const unsigned char *s;
unsigned int n;
if (!pk
|| pk->pubkey_algo != PUBKEY_ALGO_ECDH
|| !gcry_mpi_get_flag (pk->pkey[2], GCRYMPI_FLAG_OPAQUE)
|| !(s = gcry_mpi_get_opaque (pk->pkey[2], &n)) || !n)
{
gpg_err_set_errno (EINVAL);
return NULL; /* Invalid parameter */
}
n = (n+7)/8;
return bin2hex (s, n, NULL);
}