  The emerging magneto-resistive RAM (MRAM) has considerable potential to
become a universal memory technology because of its several advantages:
unlimited endurance, lower read/write latency, ultralow-power operation,
high-density, and CMOS compatibility, etc. This paper will demonstrate an
effective technique to generate random numbers from energy-efficient
consumer-off-the-shelf (COTS) MRAM chips. In the proposed scheme, the inherent
(intrinsic/extrinsic process variation) stochastic switching behavior of
magnetic tunnel junctions (MTJs) is exploited by manipulating the write latency
of COTS MRAM chips. This is the first system-level experimental implementation
of true random number generator (TRNG) using COTS toggle MRAM technology to the
best of our knowledge. The experimental results and subsequent NIST SP-800-22
suite test reveal that the proposed latency-based TRNG is acceptably fast (~22
Mbit/s in the worst case) and robust over a wide range of operating conditions.
