Authors:
Ziya Alper Genç
;
Gabriele Lenzini
;
Peter Y. A. Ryan
and
Itzel Vazquez Sandoval
Affiliation:
University of Luxembourg, Luxembourg
Keyword(s):
Honeywords, Password-based Authentication, Secure Protocols Design, Formal Analysis, ProVerif.
Abstract:
In 2013 Juels and Rivest introduced the Honeywords System, a password-based authentication system designed
to detect when a password file has been stolen. A Honeywords System stores passwords together with
indistinguishable decoy words so when an intruder steals the file, retrieves the words, and tries to log-in, he
does not know which one is the password. By guessing one from the decoy words, he may not be lucky and
reveal the leak. Juels and Rivest left a problem open: how to make the system secure even when the intruder
corrupted the login server’s code. In this paper we study and solve the problem. However, since “code corruption”
is a powerful attack, we first define rigorously the threat and set a few assumptions under which the
problem is still solvable, before showing meaningful attacks against the original Honeywords System. Then
we elicit a fundamental security requirement, implementing which, we are able to restore the Honeywords
System’s security despite a corrupted login
service. We verify the new protocol’s security formally, using
ProVerif for this task. We also implement the protocol and test its performance. Finally, at the light of our
findings, we discuss whether it is still worth using a fixed honeywords-based system against such a powerful
threat, or whether it is better, in order to be resilient against code corruption attacks, to design afresh a
completely different password-based authentication solution.
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