Why Cryptography Should Not Rely on Physical Attack Complexity by Juliane Krämer

Author:Juliane Krämer
Language: eng
Format: epub
Publisher: Springer Singapore, Singapore

For a photonic side channel attack, it is helpful to have more information about the targeted components. It is interesting to know the relation between the inverters and the individual bits they process and represent. We determined the bit order of the inverters by analyzing emission images. The bit order is shown in Fig. 4.5a. Due to the IC’s layout, the inverters form two groups, the five msb and the three lsb. Because of the distance between the two groups and the additional enable and clock signals that lie between them, measuring the emissions of both groups in a single trace would imply too much noise. Therefore, we chose to measure the 5 msb and the 3 lsb separately. The position and approximate aperture of the measurements is shown in Fig. 4.5b. We denote the respective sets of measurements with , i.e., denotes the set of the traces captured at the chip’s msb, and accordingly denotes the set of the traces captured at the chip’s lsb. To capture all traces, we needed 26 h with the first setup. Each of these traces consists of 1,000,000 averaged measurements. Since this setup required to be used in gated operation, in fact even more than 1,000,000 measurements were needed. Given that each trace was composed of 20 measurements, 20,000,000 measurements were necessary for a single trace.Table 4.8Assembly code of the AES SubBytes Operation

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