On the Theoretical Analysis of Memristor based True Random Number Generator

Emerging nano-devices like memristors display stochastic switching behavior which poses a big uncertainty in their implementation as the next-generation CMOS alternative. However, this stochasticity provides an opportunity to design circuits for hardware security. There are several examples in literature where the stochastic switching time of memristors are used as the source of entropy to build true random number generators (TRNGs). Software-based pseudo-random numbers may not be random enough for many different applications where true random numbers are a necessity. In this work, we have analyzed traditional TRNG designs that utilize memristors' switching time and evaluated them in varying operating conditions and with process variation in mind. Specifically, we have mathematically formulated how large process variation and strong temperature and voltage dependence of memristors can degrade the performance of these TRNGs. Depending on these analyses, we also have proposed a new way of designing memristive TRNG based on difference between stochastic high resistance states of a pair of memristors. Using simple probabilistic mathematics, we have evaluated our proposed method with existing ones and shown that our proposed design is robust in unfavorable environmental conditions and in the presence of large process variation where traditional TRNG bit quality degrades rapidly.