Hardware/software codesign for stream ciphers

Abstract. The ESTREAM project has identified two profiles for stream ciphers: a hardware profile and a software profile. The software profile is directly applicable to many computer systems. The hardware profile, on the other hand, does not reflect a complete system design, but instead represents a stand-alone component. In this paper we consider the integration of hardware stream ciphers in software systems for the case of Trivium, Salsa20 and Phelix. We review the different categories of hardware/software interfaces and then present performance- and implementation results for several stream-cipher configurations. Our conclusion is that the wide variety of possible hardware/software interfaces has substantial impact on the resulting performance of the design. We therefore conclude that the hardware profile should consider not only the intrinsic performance and area cost of a stream cipher, but also the required input-output bandwidth for that given encryption performance.