一类时空混沌加解密系统的安全分析

Security of chaos-based secure communications in a large community

本文安全分析文献[Phys.Rev.E 66065202(2002)]所提的一类自同步的时空混沌流密码系统.发现该高维的加解密系统在常数的驱动下将收敛到一维,使得动力学系统的复杂性大为降低.在某些特定输入区域内容,保密系统对输入状态的微小扰动不敏感.可以建立密钥和特殊输入状态间一个简单的线性关系,并依次从密钥流中恢复出密钥.基于此,提出一套选择密文攻击方法,利用系统参数和扰动前后密钥流的差异之间的依赖关系通过寻优算法破解密钥,从而攻击了上述文献所提出的基于混沌自同步的安全通信算法.

In this paper, we present an attack on a cryptosystem designed by using a spatiotemporal chaotic system. We show that the decryptiou system proposed in （Phys. Rev. E 66, 065202 （2002）） degenerates to the one-dimensional map under the constant input, and it is insensitive to the slight perturbations to input in specially selected intervals. Consequently, the attacker can use a very simple optimization algorithm to obtain the proper input value within only hundreds of iterations. Furthermore, we prove that there exits a linear dependency between the secret key and the obtained input value, so that the attacker can break this spatiotemporal chaos-based secure communication scheme easily. Both theoretical and experimental results show that the lack of security discourages the use of these cryptosystems for practical application.