Observations on TETRA Encryption Algorithm TEA-3

Abstract: We present a number of observations on 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 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. https://tosc.iacr.org/index.php/ToSC/article/view/12077

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch

References and Relationships

• Bibliographic citation: Observations on TETRA Encryption Algorithm TEA-3 ; volume:2025 ; number:1 ; year:2025 ; IACR transactions on symmetric cryptology ; 2025, Heft 1 (2025)

Contributors, Places and Time

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

Further information

• DOI: 10.46586/tosc.v2025.i1.276-308
• URN: urn:nbn:de:101:1-2503121756042.206327727484
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 15.08.2025, 7:30 AM CEST