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Three Snakes in One Hole: The First Systematic Hardware Accelerator Design for SOSEMANUK with Optional Serpent and SNOW 2.0 Modes

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 for the performance figures of each design point. 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. Our design outperforms all existing hardware (as well as software) designs of Serpent, SNOW 2.0 and SOSEMANUK, along with those of all other eSTREAM candidates.