Statistical cryptanalysis of DFT-based speech scramblers
Wen‐Whei Chang, Jeng Yih Wang, Tan Hsu Tan · International Symposium on Information Theory and its Applications · 1994
This paper presents an automated attack for cryptanalysis of transform-based analogue speech scramblers. In this system, the key estimate is recovered by embedding the discrete key in a continuous set and maximizing the statistical likelihood function over the continuous key space. Furthermore, a novel likelihood maximization algorithm has been developed to account for the doubly stochastic constraint of the underlying key space. It is shown that the proposed statistical cryptanalysis appears useful in breaking the scrambled speech under a ciphertext only attack.