Security enhancements in GSM cellular standard

GSM is widely used cellular standard in the world. GSM uses A5/x algorithms to secure the information sent over the air interface. A5/1 is a strong encryption algorithm among all A5/x algorithms. However, recent studies show that it has security flaws in its architecture, owing to which it is susceptible to several cryptographic attacks. This paper presents an enhanced scheme of A5/1 algorithm to improve the level of security provided by the GSM. Proposed scheme is analyzed against some cryptographic attacks and it is shown that the scheme provides more security by offering more resistance to correlation attack, algebraic attack and linear approximation attack. Moreover, the linear complexity of the enhanced cipher is quite large and makes the cipher to withstand the Berleykamp-Massey attack. It is also shown that the proposed scheme is little faster with respect to the output rate. Both the designs are coded in VHDL andP synthesized on FPGA device.

[1]  Emin Anarim,et al.  A modified stream generator for the GSM encryption algorithms A5/1 and A5/2 , 2005, 2005 13th European Signal Processing Conference.

[2]  염흥렬,et al.  [서평]「Applied Cryptography」 , 1997 .

[3]  Eli Biham,et al.  Cryptanalysis of the A5/1 GSM Stream Cipher , 2000, INDOCRYPT.

[4]  Cunsheng Ding,et al.  The Stability Theory of Stream Ciphers , 1991, Lecture Notes in Computer Science.

[5]  Claude Carlet,et al.  Boolean Functions for Cryptography and Error-Correcting Codes , 2010, Boolean Models and Methods.

[6]  Michalis D. Galanis,et al.  Comparison of the hardware architectures and FPGA implementations of stream ciphers , 2004, Proceedings of the 2004 11th IEEE International Conference on Electronics, Circuits and Systems, 2004. ICECS 2004..

[7]  Jovan Dj. Golic,et al.  Cryptanalysis of Alleged A5 Stream Cipher , 1997, EUROCRYPT.

[8]  Thomas Johansson,et al.  Another attack on A5/1 , 2003, IEEE Trans. Inf. Theory.

[9]  Eli Biham,et al.  Conditional Estimators: An Effective Attack on A5/1 , 2005, Selected Areas in Cryptography.

[10]  Alexander Maximov,et al.  Some Words on Cryptanalysis of Stream Ciphers , 2006 .

[11]  Alexander Maximov,et al.  An Improved Correlation Attack on A5/1 , 2004, Selected Areas in Cryptography.

[12]  Mitsuru Matsui,et al.  Linear Cryptanalysis Method for DES Cipher , 1994, EUROCRYPT.

[13]  Bernard P. Zajac.  Applied cryptography: Protocols, algorithms, and source code in C , 1994 .

[14]  Patrik Ekdahl,et al.  On LFSR based Stream Ciphers - analysis and design , 2003 .

[15]  Alex Biryukov,et al.  Real Time Cryptanalysis of A5/1 on a PC , 2000, FSE.

[16]  Palash Sarkar,et al.  Construction of Nonlinear Boolean Functions with Important Cryptographic Properties , 2000, EUROCRYPT.