-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_method() makes B<meth> the default method for all B<DH>
-structures created later.
-
-DH_get_default_method() returns a pointer to the current default
-method.
-
-DH_set_method() selects B<meth> for all operations using the structure B<dh>.
-
-DH_get_method() returns a pointer to the method currently selected
-for B<dh>.
-
-DH_new_method() allocates and initializes a B<DH> structure so that
-B<method> will be used for the DH operations. If B<method> is B<NULL>,
-the default method 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 dependent 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.