Looking for "EC_GROUP_to_params" function in OpenSSL 3

[Matt Caswell]

On 27/01/2023 10:34, Oliver Mihatsch wrote:
> Hello OpenSSL users,
> 
> I'm currently searching for the reverse operation of
> EC_GROUP_new_from_params() which should create an EC_GROUP from an
> OSSL_PARAM array in the public API.
> I need to convert an EC_GROUP back to an OSSL_PARAM array to modify it
> (in this case shift the generator/base point of the group).
> 
> A suitable function is available in 'include/crypto/ec.h' called
> ossl_ec_group_todata() but I couldn't find a way to access it via
> public API.
> 
> Is there something I've overlooked or is the counterpart function of
> EC_GROUP_new_from_params() missing in the public API?

AFAIK it is missing.

> If this the case,
> would you accept a pull request to add a function like
> EC_GROUP_to_params() which internally calls ossl_ec_group_todata()?
> 

It seems like a reasonable feature request. I can't promise it would be 
accepted but it would be looked at. Any such PR would need to target the 
master branch (it would not be acceptable for 3.1/3.0/1.1.1) and ensure 
it included appropriate documentation and tests.

Matt

> 
> Thanks a lot,
> Oliver
> 
> ------
> 
> 
> (/include/openssl/ec.h)
> EC_GROUP *EC_GROUP_new_from_params(const OSSL_PARAM params[],
>   OSSL_LIB_CTX *libctx, const char *propq);
> 
> 
> (include/crypto/ec.h)
> 
> int ossl_ec_group_todata(const EC_GROUP *group, OSSL_PARAM_BLD *tmpl,
>                           OSSL_PARAM params[], OSSL_LIB_CTX *libctx,
>                           const char *propq,
>                           BN_CTX *bnctx, unsigned char **genbuf);
> 
> int ossl_ec_group_fromdata(EC_KEY *ec, const OSSL_PARAM params[]);
> 
>