**4. Voice Encryption Algorithm Design and Its Analysis**

Chaos-based cryptography is one of the topics that has been intensively studied in recent years because of the randomness and rich dynamics of chaotic systems [53–58]. These works usually focus on image encryption. A new RNG algorithm design is performed by using the developed chaotic form and National Institute of Standards and Technology (NIST) 800-22 [59] randomness tests are employed to study the randomness of the obtained random numbers. It is noted that the NIST statistical test suit is used for the evaluation of the advanced encryption standard candidate algorithms. At first, a voice encryption algorithm is proposed using the obtained random number. Then, the voice encryption is executed by using the proposed algorithm and frequency spectrum analysis of the encryption procedure is executed.
