Impedance vs. Power Side-channel Vulnerabilities: A Comparative Study

TL;DR

This work addresses the vulnerability of cryptographic devices to unintended physical leakage by proposing and evaluating impedance-based side-channel analysis as a competitive alternative to traditional power-based attacks. The authors implement a comparative AES-128 key extraction study on memory hardware, using a memory controller and a VNA to collect impedance traces and an oscilloscope for power traces, and analyze leakage with correlation methods under both baseline and noisy conditions. They find that impedance SCA often yields higher discriminability and requires fewer traces to recover subkeys, even when power SCA fails, highlighting impedance as a more robust and potentially dangerous channel. The results motivate integrating impedance-based leakage into hardware security assessments and call for developing countermeasures that address this channel, which may persist even when devices are powered down or protected against power-based leaks.

Abstract

Physical side channels emerge from the relation between internal computation or data with observable physical parameters of a chip. Previous works mostly focus on properties related to current consumption such as power consumption. The fundamental property behind current consumption occur from the impedance of the chip. Contemporary works have stared using chip impedance as a physical side channel in extracting sensitive information from computing systems. It leverages variations in intrinsic impedance of a chip across different logic states. However, there has been a lack of comparative studies. In this study, we conduct a comparative analysis of the impedance side channel, which has been limitedly explored, and the well-established power side channel. Through experimental evaluation, we investigate the efficacy of these side channels in extracting stored advanced encryption standard (AES) cryptographic key on a memory and analyze their performance. Our findings indicate that impedance analysis demonstrates a higher potential for cryptographic key extraction compared to power side-channel analysis (SCA). Moreover, we identify scenarios where power SCA does not yield satisfactory results, whereas impedance analysis proves to be more robust and effective. This work not only underscores the significance of impedance SCA in enhancing cryptographic security but also emphasizes the necessity for a deeper understanding of its mechanisms and implications.

Figures (8)

• Figure 1: Overview of AES Encryption.
• Figure 2: Experimental setup diagram.
• Figure 3: AES key extraction method.
• Figure 4: Results of 8-bit subkey extraction for 128-bit AES.
• Figure 5: Maximum correlation coefficient without noise.