Enhanced Audio Cryptosystem Using Multiple Secret Keys and Permutations in Time and Transform Domains

This paper presents an enhanced audio speech cryptosystem based on three enhancements for permutation and substitution of speech segments using multiple secret keys and permutations in time and transform domains. The first enhancement method is based on repeating the first and last permutation steps in both encryption/decryption procedures for several times to enhance the security level. The second and third enhancement methods are based on adding two additional secret keys generated from the original key besides the utilized three keys. This adds another security layer for the modified developed audio cryptosystem. Simulation experiments demonstrated that these modifications enhance the security level and quality for the audio cryptosystem compared with a recent audio cryptosystem.