A5/1 is the symmetric cipher used for encrypting over-the-air transmissions in the GSM standard. A5/1 is used in most European countries, whereas a weaker cipher, called A5/2, is used in other countries (a description of A5/2 and an attack can be found in 4). The description of A5/1 was first kept secret but its design was reversed engineered in 1999 by Briceno, Golberg, and Wagner. A5/1 is a synchronous stream cipher based on linear feedback shift registers (LFSRs). It has a (64)-bit secret key.
A GSM conversation is transmitted as a sequence of 228-bit frames (114 bits in each direction) every (4.6) millisecond. Each frame is xored with a 228-bit sequence produced by the A5/1 running-key generator. The initial state of this generator depends on the 64-bit secret key, (K), which is fixed during the conversation, and on a 22-bit public frame number, F.
The A5/1 running-key generator (see Figure 2) consists of three LFSRs of lengths (19), (22), and (23). Their characteristic...
This is a preview of subscription content, log in via an institution.
References
Biham, E. and O. Dunkelman (2000). “Cryptanalysis of the A5/1 GSM stream cipher.” INDOCRYPT 2000, Lecture Notes in Computer Science, vol. 1977, eds. B. Roy and E. Okamoto. Springer-Verlag, Berlin, 43–51.
Biryukov, A., A. Shamir, and D. Wagner (2000). “Real time attack of A5/1 on a PC.” Fast Software Encryption 2000, Lecture Notes in Computer Science, vol. 1978, ed. B. Schneier. Springer-Verlag, Berlin, 1–18.
Ekdahl, P. and T. Johansson (2003). “Another attack on A5/1.” IEEE Transactions on Information Theory, 49 (1), 284–289.
Petrović, S. and A. Fúster-Sabater (2000). “Cryptanalysis of the A5/2 algorithm.” Cryptology ePrint Archive, Report 2000/052. Available on http://eprint.iacr.org/
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2005 International Federation for Information Processing
About this entry
Cite this entry
Canteaut, A. (2005). A5/1. In: van Tilborg, H.C.A. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA . https://doi.org/10.1007/0-387-23483-7_1
Download citation
DOI: https://doi.org/10.1007/0-387-23483-7_1
Publisher Name: Springer, Boston, MA
Print ISBN: 978-0-387-23473-1
Online ISBN: 978-0-387-23483-0
eBook Packages: Computer ScienceReference Module Computer Science and Engineering