-such as hardware accelerators may be used.
-
-Initially, the default is to use the OpenSSL internal implementation.
-DH_OpenSSL() returns a pointer to that method.
-
-DH_set_default_openssl_method() makes B<meth> the default method for all DH
-structures created later. B<NB:> This is true only whilst the default engine
-for Diffie-Hellman operations remains as "openssl". ENGINEs provide an
-encapsulation for implementations of one or more algorithms, and all the DH
-functions mentioned here operate within the scope of the default
-"openssl" engine.
-
-DH_get_default_openssl_method() returns a pointer to the current default
-method for the "openssl" engine.
-
-DH_set_method() selects B<engine> as the engine that will be responsible for
-all operations using the structure B<dh>. If this function completes successfully,
-then the B<dh> structure will have its own functional reference of B<engine>, so
-the caller should remember to free their own reference to B<engine> when they are
-finished with it. NB: An ENGINE's DH_METHOD can be retrieved (or set) by
-ENGINE_get_DH() or ENGINE_set_DH().
-
-DH_new_method() allocates and initializes a DH structure so that
-B<engine> will be used for the DH operations. If B<engine> is NULL,
-the default engine for Diffie-Hellman opertaions is used.
+such as hardware accelerators may be used. IMPORTANT: See the NOTES section for
+important information about how these DH API functions are affected by the use
+of B<ENGINE> API calls.
+
+Initially, the default DH_METHOD is the OpenSSL internal implementation, as
+returned by DH_OpenSSL().
+
+DH_set_default_method() makes B<meth> the default method for all DH
+structures created later. B<NB>: This is true only whilst no ENGINE has been set
+as a default for DH, so this function is no longer recommended.
+
+DH_get_default_method() returns a pointer to the current default DH_METHOD.
+However, the meaningfulness of this result is dependant on whether the ENGINE
+API is being used, so this function is no longer recommended.
+
+DH_set_method() selects B<meth> to perform all operations using the key B<dh>.
+This will replace the DH_METHOD used by the DH key and if the previous method
+was supplied by an ENGINE, the handle to that ENGINE will be released during the
+change. It is possible to have DH keys that only work with certain DH_METHOD
+implementations (eg. from an ENGINE module that supports embedded
+hardware-protected keys), and in such cases attempting to change the DH_METHOD
+for the key can have unexpected results.
+
+DH_new_method() allocates and initializes a DH structure so that B<engine> will
+be used for the DH operations. If B<engine> is NULL, the default ENGINE for DH
+operations is used, and if no default ENGINE is set, the DH_METHOD controlled by
+DH_set_default_method() is used.