Optically enhanced position-locked power analysis

Abstract

This paper introduces a refinement of the power-analysis attack on integrated circuits. By using a laser to illuminate a specific area on the chip surface, the current through an individual transistor can be made visible in the circuit's power trace. The photovoltaic effect converts light into a current that flows through a closed transistor. This way, the contribution of a single transistor to the overall supply current can be modulated by light. Compared to normal power-analysis attacks, the semi-invasive position-locking technique presented here gives attackers not only access to Hamming weights, but to individual bits of processed data. This technique is demonstrated on the SRAM array of a PIC16F84 microcontroller and reveals both which memory locations are being accessed, as well as their contents. © International Association for Cryptologic Research 2006.