الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
Nowadays, secure speech within communication systems has become a major concern due to the rapid development of digital networks and networking technology. VoIP, or Voice over Internet Protocol, is a technology that has been integrated into modern IP phone systems that allows callers to leave messages through a communication network.
The objective of this thesis is to increase the level of security for VoIP systems. Three approaches for voice encryption are proposed with biometric authentication.
The first one is concerned with the Secure VoIP System, based on biometric voice authentication and nested digital cryptosystem using chaotic Baker’s MAP and Arnold’s Cat MAP Encryption.
The second approach is concerned with the voice over internet protocol voicemail security system using a two-factor authentication and biometric prints with a new efficient hybrid cryptosystem.
The third approach is related to the Speech Encryption Method based on Lorenz MAP and Baker MAP. The performance evaluation measures such as correlation coefficient, spectral distortion, log likelihood ratio, time processing and histogram have ensured the efficiency of the proposed cryptosystems.
Moreover, it has been found from passing the encrypted file through Orthogonal Frequency Division Multiplexing framework with variant Signal-to-Noise Ratio that the performance evaluation measures are similar in the sender and the receiver, and this means the efficiency of encryption and decryption process.
The quality measurement results of the three approaches show that hybrid cryptosystem RC6 with Baker speech encryption provides a better result.