International Association for Cryptologic Research
Recently, the U.S national security agency has published the specifications of two families of lightweight block ciphers, simon and speck, on ePrint. The ciphers are developed with optimization towards both hardware and software in mind. While the specification paper discusses design requirements and performance of the presented lightweight ciphers thoroughly, no security assessment is given. This paper is a move towards filling that cryptanalysis gap for the simon family of ciphers. The authors present a series of observations on the presented construction that, in some cases, yield attacks, while in other cases may provide basis of further analysis by the cryptographic community.