Resilient Password Manager Using Physical Unclonable Functions

The offline dictionary attacks on the database of passwords (PW) or even hashed PW are damaging as a single server break-in leads to many compromised PWs. In this regard, using Physical Unclonable Functions (PUFs) to increase the security of PW manager systems has been recently proposed. Using PUFs allows replacing the hashed PW with PUF responses, which provide an additional hardware layer of security. In this way, even with accessing the database, an adversary should have physical control of the PUF to find the PWs. However, such a scheme cannot operate without a backup in case of catastrophic failure of the PUFs. The likelihood of a failure is low unless the opponent finds a way to destroy the PUF. The scheme used in this article includes a mechanism to make the system works consistently if the PUF fails, with redundant elements. In this method, two PUF outputs are saved in the database to register a user. In authentication, the first PUF output in the database is just checked. The second PUF output in the database is only checked in the exceptional cases when the first PUF does not work correctly; therefore, both false reject rates and latencies are not degraded. A PW manager node is implemented using a low-cost microcontroller, SRAM PUF, and nonvolatile SRAM. The nonvolatile SRAM is embedded in the PWM node circuit as a local database. Statistical tests on the applied commercial SRAM in this article show better PUF quality than those used in previous research. Also, to handle the error in PUF responses, only the stable SRAM cells are used. This article presents the first prototype of a resilient PW manager node with an embedded local database to the best of our knowledge.