+ size_t (*dirty) (const EVP_PKEY *pk);
+ void *(*export_to) (const EVP_PKEY *pk, EVP_KEYMGMT *keymgmt);
+
+dirty_cnt() returns the internal key's dirty count.
+This can be used to synchronise different copies of the same keys.
+
+The export_to() method exports the key material from the given key to
+a provider, through the L<EVP_KEYMGMT(3)> interface, if that provider
+supports importing key material.
+