The EVP_PKEY_new() function allocates an empty EVP_PKEY structure which is used by OpenSSL to
store private keys.
EVP_PKEY_free() frees up the private key key.
NOTES
The EVP_PKEY structure is used by
various OpenSSL functions which require a general private key without
reference to any particular algorithm.
The structure returned by EVP_PKEY_new() is empty. To add a private
key to this empty structure the functions described in EVP_PKEY_set1_RSA(3)
should be used.
RETURN VALUES
EVP_PKEY_new() returns either the newly allocated EVP_PKEY structure of NULL if an error occurred.