Power analysis and optimization of the ZUC stream cipher for LTE-Advanced mobile terminals

In this paper we devise and compare several hardware implementations of the confidentiality algorithm that is based on the ZUC stream cipher. First we design and analyze a reference architecture, which reflects a basic implementation of the algorithm, with respect to power and area consumption in order to identify design´s bottlenecks. Then different architectures for the most power demanding operations are explored to reduce the power consumption at the register transfer level. These architectures are evaluated at various timing constraints to account for data rates from LTE up to LTE-Advanced. The hardware analysis is done using Faraday´s 90 nm standard cell library. Our results show that 19% of power savings with 2% of area reduction can be achieved by using a cryptographic substitution box with one-hot encoding. When combining this with parallel LFSR architectures, power savings can be raised up to 37%, but with an area overhead of 10%.