Stochastic Oscillations of LaCoO₃ Memristor for True Random Number Generator

In the era of Internet of Things, information security has become significantly important. Hardware-based true random number generator (TRNG) is a crucial component of security that relies on unpredictability, and the physical stochasticity of memristors has been implemented for TRNG. Here we demonstrate LaCoO₃ memristor capable of generating random numbers using its stochastic self-oscillations. We utilized Scanning Transmission X-ray Microscopy to confirm a low to high electron-spin-state transition in the Co³⁺ ion during the insulator-metal-transition (IMT). Our LaCoO₃-based TRNG requires only one flip-flop to produce binary bits and generates the highest bit generation speed among reported volatile-memristor-based TRNGs. It successfully passed the NIST randomness test without any post-processing. Unlike Mott-transition-based memristors, such as VO₂ and NbO₂ devices, which have abrupt temperature-driven IMT, the spin-state transition of LaCoO₃ undergoes the IMT with a gradual temperature increase, leading to high endurance. This work demonstrates the advancement of memristor-based hardware security, providing a major step toward a simple, fast, and stable system.