Towards a memristive hardware secure hash function (MemHash)

Hardware based hash functions might provide a low cost and low power alternative to the classic solutions, which are based on implementations of mathematical cryptographic algorithms. In this paper, we propose MemHash, a hardware secure hash function built using memristive technology that exploits the unique properties of memristors. The MemHash operation is based on intrinsic device characteristics. Furthermore, it exploits process variations for implicit key embedding, thus creating a keyed-hash message authentication code (HMAC) that does not involve a separate key generation and management process. MemHash comprises a memristive crossbar with a differential read mechanism and a scrambler unit. The scrambler unit receives the input message as a bit stream and digitally mixes it with data read from the array. For every bit of the message, the scrambler generates a write address and a value to perform a single-cell write cycle to the crossbar. Because the crossbar is designed to be extremely sensitive to the write disturb phenomenon, every single-cell write alters additional cells in the design, thus increasing the entropy. The differential read mechanism provides sensitivity to process variations and robustness in operating conditions, yielding a PUF-like effect. MemHash is evaluated with a 16 × 16 memristive crossbar structure. Our simulation results demonstrate the statistical characteristics of the proposed design, showing close-to-optimal uniqueness and diffuseness.