Umut Topkara Mercan Topkara Mikhail J. Atallah Passwords for Everyone: Secure Mnemonic-based Accessible Authentication. 369-374 2007 conf/usenix/2007 USENIX Annual Technical Conference http://www.usenix.org/events/usenix07/tech/topkara.html db/conf/usenix/usenix2007.html#TopkaraTA07