Cryptanalysis of TETRA Encryption Algorithms - Episode 1: TEA-3

Jens Alich; Amund Askeland; Subhadeep Banik; Tim Beyne; Anne Canteaut; Patrick Felke; Gregor Leander; Willi Meier; Lukas Stennes

Paper 2024/2045

Cryptanalysis of TETRA Encryption Algorithms - Episode 1: TEA-3

Jens Alich, Ruhr University Bochum, Bochum, Germany

Amund Askeland, University of Bergen, Bergen, Norway

Subhadeep Banik, Universita della Svizzera Italiana, Lugano, Switzerland

Tim Beyne, COSIC, KU Leuven, Leuven, Belgium

Anne Canteaut, Inria, Paris, France

Patrick Felke, University of Applied Sciences Emden/Leer, Emden, Germany

Gregor Leander, Ruhr University Bochum, Bochum, Germany

Willi Meier, University of Applied Sciences and Arts Northwestern Switzerland, Windisch, Switzerland

Lukas Stennes, Ruhr University Bochum, Bochum, Germany

Abstract

We present the first public and in-depth cryptanalysis of TEA-3, a stream cipher used in TETRA radio networks that was kept secret until recently. While the same also holds for the six other TETRA encryption algorithms, we pick TEA-3 to start with as (i) it is not obviously weakened as TEA-{1,4,7} but (ii) in contrast to TEA-2 it is approved only for extra-European emergency service, and (iii) as already noted by [MBW23] the TEA-3 design surprisingly contains a non-bijective S-box. Most importantly, we show that the 80-bit non-linear feedback shift register operating on the key decomposes into a cascade of two 40-bit registers. Although this hints at an intentional weakness at first glance, we are not able to lift our results to a practical attack. Other than that, we show how the balanced non-linear feedback functions used in the state register of TEA-3 can be constructed.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Preprint.
Keywords: TETRA TEA-3 Stream cipher Cryptanalysis ETSI
Contact author(s): jens alich @ rub de
amund askeland @ uib no
subhadeep banik @ usi ch
tim beyne @ esat kuleuven be
anne canteaut @ inria fr
patrick felke @ hs-emden-leer de
gregor leander @ rub de
willimeier48 @ gmail com
lukas stennes @ rub de
History: 2024-12-19: approved; 2024-12-18: received; See all versions
Short URL: https://ia.cr/2024/2045
License: CC BY

BibTeX

@misc{cryptoeprint:2024/2045,
      author = {Jens Alich and Amund Askeland and Subhadeep Banik and Tim Beyne and Anne Canteaut and Patrick Felke and Gregor Leander and Willi Meier and Lukas Stennes},
      title = {Cryptanalysis of {TETRA} Encryption Algorithms - Episode 1: {TEA}-3},
      howpublished = {Cryptology {ePrint} Archive, Paper 2024/2045},
      year = {2024},
      url = {https://eprint.iacr.org/2024/2045}
}