Towards Generating True Random Numbers using Magnetoresistive RAM

Generating random numbers is a critical task in any security-related scenario, e.g., generating secure cryptographic keys for communication. Pseudo Random Number Generators (PRNG) do fulfill the task of generating numbers, though they are fundamentally dependent on a random seed or an entropy source. True Random Number Generators (TRNG) use other sources of entropy to generate a truly random number, e.g., by measuring the radioactive decay of an atom or electrostatic interference. This paper proposes a novel way of generating truly random numbers by leveraging the nondeterministic write behavior of Magnetoresistive Random Access Memory (MRAM) that occurs, if an external magnetic field is applied during operation. Since the MRAM chips are manufactured with nanoscale impurities on silicon level, it acts as a Physically Unclonable Function (PUF) and can be employed in security critical applications. For that, a formal description of the algorithm and technical details are thoroughly described. To show the true randomness of the operation, we provide a statistical significance evaluation which is based on real-world experiments. The results show that the MRAM behaves significantly nondeterministic while also providing an entropy of over 0.99 among all tested boards.