Paper 2013/404 The SIMON and SPECK Families of Lightweight Block Ciphers Ray Beaulieu, Douglas Shors, Jason Smith, Stefan Treatman-Clark, Bryan Weeks, and Louis Wingers Abstract In this paper we propose two families of block ciphers, SIMON and SPECK, each of which comes in a variety of widths and key sizes. While many lightweight block ciphers exist, most were designed to perform well on a single