# ANALYSIS OF SNOW 3G⊕ RESYNCHRONIZATION MECHANISM

### Alex Biryukov, Deike Priemuth-Schmid, Bin Zhang

#### Abstract

The stream cipher SNOW3G designed in 2006 by ETSI/SAGE is a base algorithm for the second set of 3GPP confidentiality and integrity algorithms. This paper is the first attempt of cryptanalysis of this algorithm in the public literature. We look at SNOW 3G in which two modular additions are replaced by xors, which is called SNOW 3G⊕. We show that the feedback from the FSM to the LFSR is very important, since we can break a version without such a feedback using a pair of known IVs with practical complexities (257 time and 233 keystream). We then extend this technique into a differential chosen IV attack on SNOW 3G⊕ and show how to break 16 out of 33 rounds with the feedback.

#### References

- Billet, O. and Gilbert, H. (2005). Resistance of SNOW 2.0 Against Algebraic Attacks. In Topics in CryptologyCT-RSA'2005. LNCS vol. 3376, pp. 19-28. SpringerVerlag 2005.
- Ekdahl, P. and Johansson T. (2002). A New Version of the Stream Cipher SNOW. In Selected Areas in Cryptography-SAC 2002. LNCS vol. 1233, pp. 37-46. Springer-Verlag 2002.
- ETSI/SAGE. (2006). Specification of the 3GPP Confidentiality and Integrity Algorithms UEA2 & UIA2. Document 2: SNOW 3G Specification, version 1.1 In September 2006. http://www.3gpp.org/ftp/..
- ETSI/SAGE (2006). Specification of the 3GPP Confidentiality and Integrity Algorithms UEA2 & UIA2. Document 5: Design and Evaluation Report, version 1.1 In September 2006. http://www.3gpp.org/ftp/.
- Nyberg, K. and Wallén, J. (2006). Improved Linear Distinguishers for SNOW 2.0. In Fast Software EncryptionFSE 2006. LNCS vol. 4047, pp. 144-162. SpringerVerlag 2006.
- Watanabe, D., Biryukov, A., De Cannière, Christophe, (2004). A Distinguishing Attack of SNOW 2.0 with Linear Masking Method. In Selected Areas in Cryptography-SAC 2003. LNCS vol. 3006, pp. 222- 233. Springer-Verlag 2004.

#### Paper Citation

#### in Harvard Style

Biryukov A., Priemuth-Schmid D. and Zhang B. (2010). **ANALYSIS OF SNOW 3G⊕ RESYNCHRONIZATION MECHANISM** . In *Proceedings of the International Conference on Security and Cryptography - Volume 1: SECRYPT, (ICETE 2010)* ISBN 978-989-8425-18-8, pages 327-333. DOI: 10.5220/0002926603270333

#### in Bibtex Style

@conference{secrypt10,

author={Alex Biryukov and Deike Priemuth-Schmid and Bin Zhang},

title={ANALYSIS OF SNOW 3G⊕ RESYNCHRONIZATION MECHANISM},

booktitle={Proceedings of the International Conference on Security and Cryptography - Volume 1: SECRYPT, (ICETE 2010)},

year={2010},

pages={327-333},

publisher={SciTePress},

organization={INSTICC},

doi={10.5220/0002926603270333},

isbn={978-989-8425-18-8},

}

#### in EndNote Style

TY - CONF

JO - Proceedings of the International Conference on Security and Cryptography - Volume 1: SECRYPT, (ICETE 2010)

TI - ANALYSIS OF SNOW 3G⊕ RESYNCHRONIZATION MECHANISM

SN - 978-989-8425-18-8

AU - Biryukov A.

AU - Priemuth-Schmid D.

AU - Zhang B.

PY - 2010

SP - 327

EP - 333

DO - 10.5220/0002926603270333