Following the MNet documentation to have two Moodle sites talk to one another, I am getting the following error when I go to the "Services" tab of a peer while following the setup steps described in "2. Get user roaming going":

OpenSSL unable to seal data

Debug info:
Error code: opensslsealerror

Stack trace:
line 294 of /mnet/lib.php: core\exception\moodle_exception thrown
line 143 of /mnet/xmlrpc/client.php: call to mnet_encrypt_message()
line 820 of /mnet/lib.php: call to mnet_xmlrpc_client->send()
line 39 of /admin/mnet/services_form.php: call to mnet_get_service_info()
line 217 of /lib/formslib.php: call to mnet_services_form->definition()
line 41 of /admin/mnet/services.php: call to moodleform->__construct()