Cryptology ePrint Archive: Report 2012/696

Cryptanalysis of RAKAPOSHI Stream Cipher

Lin Ding and Jie Guan

Abstract: RAKAPOSHI is a hardware oriented stream cipher designed by Carlos Cid et al. in 2009. The stream cipher is based on Dynamic Linear Feedback Shift Registers, with a simple and potentially scalable design, and is particularly suitable for hardware applications with restricted resources. The RAKAPOSHI stream cipher offers 128-bit security. In this paper, we point out some weaknesses in the cipher. Firstly, it shows that there are 2^192 weak (key, IV) pairs in RAKAPOSHI stream cipher. Secondly, for weak (key, IV) pairs of RAKAPOSHI, they are vulnerable to linear distinguishing attack and algebraic attack. Finally, we propose a real time related key chosen IV attack on RAKAPOSHI. The attack on RAKAPOSHI recovers the 128-bit secret key of with a computational complexity of 2^37, requiring 47 related keys, 2^8 chosen IVs and 2^14.555 keystream bits. The success probability of this attack is 0.999, which is quite close to 1. The experimental results corroborate our assertion.

Category / Keywords: secret-key cryptography / Cryptanalysis; linear distinguishing attack; algebraic attack; related key chosen IV attack; RAKAPOSHI; stream cipher.

Publication Info: The paper had been submitted and is under review now.

Date: received 11 Dec 2012

Contact author: dinglin_cipher at 163 com

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Version: 20121214:195322 (All versions of this report)

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