Fast Software Encryption

Volume 6147 of the series Lecture Notes in Computer Science pp 1-18

Cryptanalysis of the DECT Standard Cipher

  • Karsten NohlAffiliated withUniversity of Virginia
  • , Erik TewsAffiliated withTechnische Universität Darmstadt
  • , Ralf-Philipp WeinmannAffiliated withUniversity of Luxembourg


The DECT Standard Cipher (DSC) is a proprietary 64-bit stream cipher based on irregularly clocked LFSRs and a non-linear output combiner. The cipher is meant to provide confidentiality for cordless telephony. This paper illustrates how the DSC was reverse-engineered from a hardware implementation using custom firmware and information on the structure of the cipher gathered from a patent. Beyond disclosing the DSC, the paper proposes a practical attack against DSC that recovers the secret key from 215 keystreams on a standard PC with a success rate of 50% within hours; somewhat faster when a CUDA graphics adapter is available.


DECT DECT Standard Cipher stream cipher cryptanalysis linear feedback shift register