On Tue, 2022-01-04 at 02:33 +0100, Wolf wrote: > Thank you for the answer! > > On 2022-01-03 10:11:19 +0100, Tomas Mraz wrote: > > You're using the secp384r1 curve which is a prime field curve. The > > OSSL_PKEY_PARAM_EC_CHAR2_M parameter can be obtained only for > > binary > > field curves. > > > > If you have a group NID for the curve of the EC key, you could use: > > > > EC_GROUP *group = EC_GROUP_new_by_curve_name_ex(NULL, NULL, nid); > > > > to create the group to call EC_GROUP_get_degree() on. > > > > Of course if you can have an EC key with arbitrary explicit group > > parameters, that would not work. > > That is sadly the case of me. > > > But you can then use number of bits of the OSSL_PKEY_PARAM_EC_P > > parameter as the degree for prime field curves. > > So, I've tried following your advice, but for some reason it is still > failing for me. I've modified my example program to be: You need to use EVP_PKEY_get_bn_param() to get the P parameter and BN_num_bits() to count the number of bits of the P value. -- Tomáš Mráz, OpenSSL
