The Hill: Researchers discover flaw in 2G mobile encryption algorithm | TheHill

[grarpamp]

> https://thehill.com/policy/technology/558815-researchers-discover-flaw-in-2g-mobile-encryption-algorithm

Please post the long and direct links to source material,
not useless shortlinks expiring and "news" sites wasting
readers to do work of poster to search click etc.

https://eprint.iacr.org/2021/819

Cryptology ePrint Archive: Report 2021/819

Cryptanalysis of the GPRS Encryption Algorithms GEA-1 and GEA-2

Christof Beierle and Patrick Derbez and Gregor Leander and Gaëtan
Leurent and Håvard Raddum and Yann Rotella and David Rupprecht and
Lukas Stennes

Abstract: This paper presents the first publicly available
cryptanalytic attacks on the GEA-1 and GEA-2 algorithms. Instead of
providing full 64-bit security, we show that the initial state of
GEA-1 can be recovered from as little as 65 bits of known keystream
(with at least 24 bits coming from one frame) in time 240 GEA-1
evaluations and using 44.5 GiB of memory. The attack on GEA-1 is based
on an exceptional interaction of the deployed LFSRs and the key
initialization, which is highly unlikely to occur by chance. This
unusual pattern indicates that the weakness is intentionally hidden to
limit the security level to 40 bit by design.

In contrast, for GEA-2 we did not discover the same intentional
weakness. However, using a combination of algebraic techniques and
list merging algorithms we are still able to break GEA-2 in time 245.1
GEA-2 evaluations. The main practical hurdle is the required knowledge
of 1600 bytes of keystream.

Category / Keywords: secret-key cryptography / GPRS Encryption, Stream
Cipher, Algebraic attacks, GEA

Original Publication (in the same form): IACR-EUROCRYPT-2021
DOI: 10.1007/978-3-030-77886-6_6
Date: received 15 Jun 2021

Contact author: christof beierle at rub de, patrick derbez at irisa fr,
gregor leander at rub de, gaetan leurent at inria fr, haavardr at simula no,
yann rotella at uvsq fr, david rupprecht at rub de, lukas stennes at rub de

Available format(s): PDF | BibTeX Citation
Version: 20210616:133848 (All versions of this report)
Short URL: ia.cr/2021/819