Transactions on Machine Intelligence 2821-1693 4 2 2021 06 01 Speech Signal Encryption in Time and Frequency Domains Using Chaotic Maps 70 75 209211 10.47176/TMI.2021.70 EN J. Shirazi Assistant Professor, Department of Electrical Engineering, Gonabad Branch, Islamic Azad University, Razavi Khorasan, Gonabad, Iran Journal Article 2021 02 24 In this paper, with the aim of enhancing the security of speech signal transmission, a method based on encrypting speech signal frames in both time and frequency domains using a chaotic map is presented. To increase the complexity of the encryption, two stages of encryption in the time domain and one stage in the frequency domain were performed on the speech signal. In the first stage, the bytes of the speech signal were altered using random numbers generated from a chaotic map, and in the second stage, the resulting samples were scrambled based on random numbers. Discrete Cosine Transform (DCT) was then applied to the resulting samples, followed by scrambling based on random numbers. To further enhance encryption security, the sequence of random numbers used was periodically altered according to a specific order to increase the complexity of the encryption detection. Various criteria were used to evaluate the employed method, and the results indicate high levels of these criteria for the method. One advantage of the used method is its complexity due to combining time and frequency domains and the multi-stage nature of the encryption. https://www.tmachineintelligence.ir/article_209211_948ba442b7ebe1152b2dcee8637201a4.pdf