Emerging non-volatile memory (NVM) technologies, such as resistive RAM (ReRAM), ferroelectric RAM (FRAM), and magnetoresistive RAM (MRAM), are gaining traction due to their scalability, energy efficiency, and resilience to traditional charge-based attacks. Unlike conventional memories that store data as electrical charge, these NVMs encode information through distinct impedance states. While this fundamental shift in data storage has led to the assumption that such memories are inherently more secure, we demonstrate that impedance itself can serve as a side-channel leakage source. In this work, we introduce and validate a novel impedance-based side-channel attack that exploits the correlation between stored data and NVM cell impedance, enabling non-invasive data extraction via power distribution network measurements. Using template construction and scattering parameter analysis, we evaluate a range of commercial ReRAM, FRAM, and MRAM devices. Our results reveal statistically significant impedance variations tied to both inter- and intra-Hamming weight differences, confirming that data-dependent impedance leakage is a real and exploitable phenomenon. These findings expose a new class of hardware vulnerabilities in emerging memory systems and highlight the need for dedicated countermeasures against impedance side channels.
