Side-Channel-Attack Resistant AES Design Based on Finite Field Construction Variation

The Advanced Encryption Standard (AES) is the current standard for symmetric key ciphers and is algorithmically secure. Side channel attacks that target power consumption can reveal the secret key in AES implementations. Masking data with random variables is one of the main methods used to thwart power analysis attacks. Data can be masked with multiple random variables to prevent higher-order attacks at the cost of a large increase in area. This thesis tests the plausibility of using varied finite field construction to prevent power analysis attacks as an alternative to masking. Initially, a design using finite field architecture as the sole countermeasure was investigated. This was followed by varied field construction in conjunction with a low entropy masking scheme. Neither approach provided an acceptable trade off between security and area. Analysis then turned to a combined Boolean and multiplicative masking scheme. Varied construction provided little gain for multiplicative masking. However, varied constructions were found to greatly increase security when used in conjunction with a Boolean random mask. A novel masking scheme for AES resistant to second-order attacks is proposed. Instead of an additional mask, variation in finite field construction is exploited to increase resistance to second-order attacks in Boolean masked shares. As a result, the area requirement is substantially reduced. For an example AES encryption, the proposed design is 12% smaller compared to the previous best design, with a small drop in achievable security level.