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Top1. Introduction
One-way hash function is a fundamental technique for information security, and it is usually applied for integrity protection, digital signatures and message authentication. In the past few years, chaos has been found that it has great potential to be used in the construction of hash function due to its sensitivity to initial conditions and system parameters, ergodicity and random like behavior. Thus, many works have been done on the chaos-based hash functions (Akhavan & Samsudin, 2009; Ren & Wang, 2009; Xiao & Liao, 2008; Zhang &Wang, 2007). Among them, wide attention has been paid to parallel hash function, where the sub-blocks of a message are processed in a parallel mode with high efficiency (Xiao & Liao, 2008). However, cryptanalysis of chaos-based hash functions is also developed very fast. Some chaos-based hash functions also been ben proved to be insecure (Li & Li 2006; Guo & Wang, 2009; Wang & Li, 2012; Wang & Wang, 2008; Wang & Xu, 2010; Wang & Zhao, 2010). Collisions and flaws exist if two or more distinct messages or keys are found to obtain a same hash value, which can be implemented by adversary to fabricate fake messages. For this reason, collision resistance is a basic requirement for a secure hash function.
Recently, a parallel hash function based on chaotic maps with changeable parameters is proposed by Li et al. (2011). Detailed analysis is performed to it, and it is found that it is vulnerable to collision attacks, thus, some measurements of how to improve its security are proposed in this paper.
The rest of the paper is organized as follows. The original algorithm is described and analyzed in the second Section 2, and some improvements are made in Section 3. In Section 4, the experiments and analysis are performed to evaluate the performance of the improved hash function. Finally, some conclusions are drawn in the Section 5.