Simon and Speck are families of lightweight block ciphers, each of which comes in a variety of widths and key sizes. The aim of Simon and Speck is to fill the need for secure, flexible, and analyzable lightweight block ciphers that perform well on a wide range of current and future platforms.
This site hosts general information about the algorithms with pointers to more detailed information available in other repositories or papers.
NEW: An update on Simon and Speck (6 Mar 2019)