Power Consumption versus Hardware Security: Feasibility Study of Differential Power Attack on Linear Feedback Shift Register Based Stream Ciphers and Its Countermeasures

This paper demonstrates a trade off between the security of a crypto-system and its power consumption. Digital stream ciphers are extensively employed in Crypto-systems. Many of them use linear feedback shift registers (LFSRs) as building blocks, wherein, an n-degree primitive connection polynomial is used as a feedback function to realize an n-bit LFSR. Using finite-field theory and electromagnetic-circuit theory, we show that such LFSRs are susceptible to differential power attacks (DPAs), without the adversary's prior knowledge of the primitive polynomial. It is interesting to note that the DPA becomes more prominent with technology scaling due to increased contribution of local interconnect to total power. The paper also presents two countermeasures for the proposed DPA that results in a trade off with power consumption. With the growing need for crypto-systems in low-power Internet-of-Things (IoTs) devices, this case study highlighting a power-security trade off is of great significance.