Paper 2021/829
To Shift or Not to Shift: Understanding GEA-1
Christof Beierle and Patrick Felke and Gregor Leander
Abstract
In their Eurocrypt 2021 paper, Beierle et al. showed that the proprietary stream ciphers GEA-1 and GEA-2, widely used for GPRS encryption in the late 1990s and during the 2000s, are cryptographically weak and presented attacks on both algorithms with practical time complexity. Although GEA-1 and GEA-2 are classical stream ciphers, the attack on GEA-1 is interesting from a cryptanalytic point of view. As outlined in the aforementioned paper, there is a strong indication that the security of GEA-1 was deliberately weakened to 40 bits in order to fulfill European export restrictions. In this paper we analyze the design further and answer the open question on how to construct a GEA-1-like cipher with such a reduced security. Indeed, the actual GEA-1 instance could be obtained from this construction. Our observations and analysis yields new theoretical insights in designing secure stream ciphers.
Metadata
- Available format(s)
- Category
- Secret-key cryptography
- Publication info
- Preprint. MINOR revision.
- Keywords
- cryptanalysisGPRSGEA-1stream cipherLFSR40-bit security
- Contact author(s)
-
christof beierle @ rub de
patrick felke @ hs-emden-leer de
gregor leander @ rub de - History
- 2022-08-10: revised
- 2021-06-21: received
- See all versions
- Short URL
- https://ia.cr/2021/829
- License
-
CC BY