SRAM Has No Chill: Exploiting Power Domain Separation to Steal On-Chip Secrets

Abstract

The widespread use of embedded systems has increased the risk of physical memory disclosure attacks. A notable example is the cold boot attack, where attackers exploit DRAM’s temperature-dependent data retention property. At low temperatures, DRAM cells temporarily retain their state after power loss, allowing sensitive data to be recovered. Cold boot attacks can expose system secrets, bypassing defenses like disk encryption. To counter this threat, developers store sensitive data in on-chip SRAM. Unlike DRAM, on-chip SRAM is isolated from external access and, due to its low capacitance, loses data almost immediately when powered off, making it robust against such attacks.

While SRAM protects against traditional cold boot attacks, we show that there is another way to retain information in on-chip SRAM across power cycles. This paper presents Volt Boot, an attack that demonstrates a vulnerability of on-chip SRAM due to the physical separation common in modern system-on-chip power distribution networks. Volt Boot leverages asymmetrical power states (for example, on vs. off) to force SRAM state retention across power cycles, eliminating the need for traditional cold boot attack enablers, such as lowtemperature or intrinsic data retention time. Using three modern ARM Cortex-A SoCs, we demonstrate the effectiveness of the attack in caches, registers, and iRAMs. Unlike other forms of SRAM data retention attacks, Volt Boot retrieves data with 100% accuracy—without any complex post-processing.