Optically Enhanced Position-Locked Power Analysis

Abstract

Abstract. This paper introduces a re¯nement of the power-analysis at-tack on integrated circuits. By using a laser to illuminate a speci¯c area on the chip surface, the current through an individual transistor can be made visible in the circuit's power trace. The photovoltaic e®ect converts light into a current that °ows 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 ac-cessed, as well as their contents. Key words: side-channel attacks, power analysis, semi-invasive attacks, optical probing