With increasing usage of hardware accelerators in modern heterogeneous
System-on-Chips (SoCs), the distinction between hardware and software is no longer rigid. The domain of cryptography is no exception and efficient hardware design of so-called software ciphers are becoming increasingly popular. In this paper, for the first time we propose an efficient hardware accelerator design for SOSEMANUK, one of the finalists of the eSTREAM stream cipher competition in the software category. Since SOSEMANUK combines the design principles of the block cipher Serpent and the stream cipher SNOW 2.0, we make our design
flexible to accommodate the option for independent execution of Serpent and SNOW 2.0. In the process, we identify interesting design points and explore different levels of optimizations. We perform a detailed experimental evaluation of the performance figures of each design point and in each case our figures by far outperform the existing benchmarks. The best throughput achieved by the combined design is 67.84 Gbps for SOSEMANUK, 33.92 Gbps for SNOW 2.0 and 2.12 Gbps for Serpent. The throughput for SOSEMANUK by far outperforms all existing benchmarks on the eSTREAM candidates.