On 25/10/2022 00:21, Kory Hamzeh wrote:
I haven’t done exactly what you are trying, but something similar.

  See EVP_PKEY_set_params:

https://www.openssl.org/docs/man3.0/man3/EVP_PKEY_set_params.html <https://www.openssl.org/docs/man3.0/man3/EVP_PKEY_set_params.html>

The specific parm to set the group could be set like this:

  OSSL_PARAM_BLD_push_utf8_string(param_bld, "group",
                                             curve, 0;

"group" is not a "settable" parameter for EC keys. You can "get" it. You can import it (using EVP_PKEY_from_data()). You can export it (using EVP_PKEY_to_data()). But you can't "set" it.

The group is immutable once the key is created.

It really doesn't make sense to change the group of a key from one thing to another. None of the rest of the parameters would be valid if the group changed.

On 25/10/2022 00:35, Martin via openssl-users wrote:
> Thanks for your response. I want to preserve the rest of the EC public
> key params. I did this. I haven’t test yet.

Preserving the rest of the EC public key params doesn't make sense. If the group has changed the key is no longer valid. Just create a new key instead.


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