EVP_PKEY_todata, EVP_PKEY_export - functions to return keys as an array of key parameters

       Copyright 2021-2025 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance
       with the License.  You can obtain a copy in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.5.0                                              2025-06-04                              EVP_PKEY_TODATA(3SSL)

       The functions described here are used to extract EVP_PKEY key values as an array of OSSL_PARAM(3).

       EVP_PKEY_todata() extracts values from a key pkey using the selection.  selection is described in
       "Selections" in EVP_PKEY_fromdata(3).  OSSL_PARAM_free(3) should be used to free the returned parameters
       in *params.

       EVP_PKEY_export() is similar to EVP_PKEY_todata() but uses a callback export_cb that gets passed the
       value of export_cbarg.  See openssl-core.h(7) for more information about the callback. Note that the
       OSSL_PARAM(3) array that is passed to the callback is not persistent after the callback returns. The user
       must preserve the items of interest, or use EVP_PKEY_todata() if persistence is required.

       These functions were added in OpenSSL 3.0.

       Support for ML-DSA, ML-KEM and SLH-DSA was added in OpenSSL 3.5.

       EVP_PKEY_todata, EVP_PKEY_export - functions to return keys as an array of key parameters

       These functions only work with key management methods coming from a provider.  This is the mirror
       function to EVP_PKEY_fromdata(3).

EVP_PKEY_todata() and EVP_PKEY_export() return 1 for success and 0 for failure.

OSSL_PARAM(3), openssl-core.h(7), EVP_PKEY_fromdata(3), EVP_PKEY-RSA(7), EVP_PKEY-EC(7), EVP_PKEY-DSA(7),
       EVP_PKEY-ED25519(7) EVP_PKEY-ED448(7), EVP_PKEY-DH(7), EVP_PKEY-X25519(7), EVP_PKEY-X448(7),
       EVP_PKEY-ML-DSA(7), EVP_PKEY-ML-KEM(7), EVP_PKEY-SLH-DSA(7).

        #include <openssl/evp.h>

        int EVP_PKEY_todata(const EVP_PKEY *pkey, int selection, OSSL_PARAM **params);
        int EVP_PKEY_export(const EVP_PKEY *pkey, int selection,
                            OSSL_CALLBACK *export_cb, void *export_cbarg);