This paper carries out a further cryptanalysis of two Lorenz-based masking secure communication systems, which have been recently attacked by a high-pass filter. As demonstrated with our simulations, high-pass filter attack works well only when the covered information signal is monotonic. However, with an adaptive observer, it is still possible to coarsely obtain the information signal and correctly identify the system user-defined parameters if a multitonic information signal is transmitted, making the security of these two systems questionable.
['Ying Liu', 'Wallace Kit-Sang Tang']
Cryptanalysis of Chaotic Masking Secure Communication Systems Using an Adaptive Observer