National University of Singapore
The core of the 3rd Generation Partnership Project (3GPP) encryption standard 128-EEA3 is a stream cipher called ZUC. It was designed by the Chinese Academy of Sciences and proposed for inclusion in the cellular wireless standards called "Long Term Evolution" or "4G". The LFSR-based cipher uses a 128-bit key. In this paper, the authors first show timing attacks on ZUC that can recover, with about 71.43% success rate; one bit of the secret key immediately, and information involving 6 other key bits. The time, memory and data requirements of the attacks are negligible. While they see potential improvements to the attacks, they also suggest countermeasures.