International Association
for Cryptologic Research

The DECT Standard Cipher (DSC) is a proprietary stream cipher used for encryption in the Digital Enhanced Cordless Telecommunications (DECT), which is a standard for short range cordless communication and widely deployed worldwide both in residential and enterprise environments. New weaknesses of the DSC stream cipher which are not discovered in previous works are explored and analyzed in this paper. Based on these weaknesses, new practical key recovery attacks and distinguishing attack on DSC with lower time cost are proposed. The first cryptanalytic result show that DSC can be broken in about 13.12 seconds in the known IV setting, when an offline phase that takes about 58.33 minutes is completed. After then, a distinguishing attack on DSC in the related key chosen IV setting is given, which has a time complexity of only 2 encryptions and a success probability of almost 1. Finally, based on the slide property, a key recovery attack on DSC with practical complexities is proposed. The experimental result shows that DSC can be broken on a common PC within about 44.97 seconds in the multiple related key setting. The attacks on DSC proposed in this paper clearly show that a well-designed initialization is absolutely necessary to design a secure stream cipher.