Question about EVP API interaction

[Juan di Mauro]

Dear all,

I'm coding an external provider for OpenSSL to incorporate a KEM algorithm
(the provider will be compiled as a .so as usual). I have the KEM part of
the code
and the Key management module (the OSSL_ALGORITHM dispatch tables and so
on, corresponding to the OSSL_OP_KEM and OSSL_OP_KEYMGMT query types).

However, I have problems making things interact ok. It's clear that
I do not fully understand the way the API should work in this case so my
first question is: Is there a complete documented guide about that?

Secondly, to state things clearly: I want to make key encapsulation and I'm
following this sequence of API calls to interact with my provider:


 EVP_PKEY_CTX *ctx;
 ctx = EVP_PKEY_CTX_new_from_name(libctx,<Name of my Keymgmt
algorithm>,NULL);
    if (!ctx){
        printf("The context can't be created. Exiting\n");
        return -1;
    }
    //generate the key
    EVP_PKEY *key = NULL;
    EVP_PKEY_keygen_init(ctx);
    EVP_PKEY_keygen(ctx, &key);
    // Here, since the pkey in context is NULL, fails
    int res_encaps_init = EVP_PKEY_encapsulate_init(ctx,NULL);


So, maybe the sequence of steps is wrong or my code doesn't satisfy the API
requirements.

Thanks in advance,

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