الفهرس 
NETWORK SECURITYOnly 14 pages are availabe for public view
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Abstract
In the last few years, computer networks are becoming more dispersed and widespread, given the impact the internet has had on extending the network out to roaming users, business partners, to transfer various types of data with different confidentiality levels. So, it is extremely important to fmd more secure and confidential methods to ensure the integrity and confidentiality of transferred data. Internet Protocol Security or IPSec is a developed mechanism, has been in use for a number of years now to protect sensitive data as it flows from one location to another depending on a set of protocols and cryptographic algorithms. So, it is a need to develop new cryptographic systems to assure’ the integrity and confidentiality of transmitted data and withstood the attacks developed methods.
Studying the cryptographic systems and the new modified algorithms, among those modified algorisms, the signcryption algorithm which came to combine between the public cryptography algorithm and the signature algorisms in one step instead of the traditional approach, signature - then - encryption, with saving in the communication overhead reach 40% and saving in computation costs reach 58% with achieving the security goals. Discuss signcryption algorithm in broadcasting one message to multiply recipients.
In this thesis, introducing a new modified scheme ”Modified Elliptic Curve Signcryption” this scheme based on Elliptic Curve Discrete Logarithm Problem (ECDLP) and in addition to achieve the functionality of the signcryption schemes, unjorgeability, confidentiality and non - repudiation, it achievesjorward security and encrypted message authentication and public verifiability .Also, using a strong session key encryption depends on using a random chosen value plus to the private key of the sender and it is used to encrypt the message twice to increase the confidentiality and integrity of the message. Although proposed scheme is slower than the Zheng’s signcryption scheme, it achieves saving in communication overhead reach 50% with respect to the traditional approach signature - then - encryption. And applying the modified scheme on multiply recipients and compare it with Zheng’s signcryption for multi - recipients. For future work, can apply the modified scheme on the IPSec mechanism to save Bandwidth and benefit with its security attributes.