SuperVAULT: Superparamagnetic Volatile Auxiliary Tamper-Proof Storage

Abstract

Memory security has recently come into the spotlight as attackers have stepped up their efforts to gain illicit access to sensitive data or cause denial-of-memory-service via a variety of avenues like cold boot attacks, bus snooping, and physical probing or tampering. In this paper, we propose SuperVAULT, a novel secure storage solution for protecting secret data/keys by exploiting the superparamagnetic regime of nanomagnets. Through materials and dimensional engineering of the magnetic tunnel junction (MTJ) free layer, the energy barrier of spintransfer torque magnetoresistive random access memory (STTMRAM) cells can be designed to lie in the range of the thermal energy (kBT ). Such superparamagnetic MTJ (s-MTJ) cells, with an O(10 ns) retention time, need to be refreshed frequently. In the absence of data refresh (under attack conditions), the data they hold is thermally corrupted to a random state after an arbitrary but short amount of time. We leverage this property to devise a secure memory primitive and showcase its potential against cold boot and Boolean satisfiability (SAT) attacks. Further, the overheads for s-MTJ-based STT-MRAMs is shown to be promising for on-chip implementations.