Welcome to the resource topic for 2024/2045
Title:
Cryptanalysis of TETRA Encryption Algorithms - Episode 1: TEA-3
Authors: Jens Alich, Amund Askeland, Subhadeep Banik, Tim Beyne, Anne Canteaut, Patrick Felke, Gregor Leander, Willi Meier, Lukas Stennes
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.
ePrint: https://eprint.iacr.org/2024/2045
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