http://wikipewt4n75trifcse2ggaieot27svognl7idu6xmmqn37kf64rvsyd.onion/index.php/Intrusive_Surveillance
If you trust Apple (and your sysadmin, where applicable), and really believe there is no master password set, you can use the built-in FileVault feature to encrypt your entire home directory with 128 bit AES, or you can attempt to do it yourself. Given the amount of work involved in doing it yourself , I would suggest trusting Apple and going the FileVault route.