In this paper we propose a new block cipher, DESL (DES Lightweight), which is based on the classical DES (Data Encryption Standard) design, but unlike DES it uses a single S-box repeated eight times.1 On this account we adapt well-known DES S-box design criteria, such that they can be applied to the special case of a single S-box. Furthermore, we show that DESL is resistant against certain types of the most common attacks, i.e., linear and differential cryptanalyses, and the Davies-Murphy attack. Our hardware implementation results of DESL are very promising (1848 GE), therefore DESL is well suited for ultraconstrained devices such as RFID tags.