الفهرس 
Introduction to Computer NetworksOnly 14 pages are availabe for public view
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Abstract
Nowadays computer networks are widely used with different scales in a lot of fields in our life. One of important network protocols is the IP protocol. The first version of the IP protocol is IPv4, then the next developed generation is IPv6. IPv6 provides enhancement fu.Octions over the IPv4 like providing more available addresses for source and destination. The IP protocol provides its network control information within its header which encapsulates the data segment to form the IP packet. The IP protocol could be adjusted to provide an optional feature called packet fragmentation. If the IP datagram crosses an interface with a maximum transmission unit smaller than its size, then the packet could be optionally fragmented so that the resulted fragments would be reassembled at the receiver. We first present a quick view for data communication in networks, the architecture of the IP header and the IP packet fragmentation! reassembly mechanism.
The main object of this thesis is to secure the content of sensitive data as some banking, military and other secure data during transmission across the network to save it from being monitored, captured, analyzed, altered or affected by any attack. Therefore; the thesis concerns about three of the famous used tools for this object which are data encryption, IPsec protocol and steganography which is the art and science of hiding data in a carrier.
About data encryption, the thesis explains the modular exponentiation cipher as one example of the strong encryption algorithms and we suggest its usage with modulus 257 to limit the ciphertext results within the decimal range which is less than 256 to be able to present them in the form of the 8-bit binary representation. Then the thesis suggests a new encryption method based on the form and properties of the Kharaghani array of order 8.
After that; the thesis provides an overview about the IPsec security services, headers, modes and fragmentation.
About steganography, the thesis concerns on using the IP datagram as a stego object to carry the hidden data. First we provide some steganographic concepts and examples for some steganographic methods which their data hiding concept depends on either embedding the covert message in some fields of the IP header which are related to defining the operation of the fragmentation feature or introducing the hidden data by modifying the packet’s fragments.
Thanks to Allah; the thesis successfully suggests some new steganographic methods. First the thesis suggests a new steganographic method for data hiding in the IP ID field of the IP header, then it suggests a new steganographic marking method with two scenarios to mark the IP stego datagrams to help the steganogram receiver in identifying them if they were mixed with normal IP datagrams in the traffic stream. Then the thesis suggests two new steganographic methods for data hiding in the payloads of marked IP datagrams. One method hides data in the payloads of marked IP packets while the other method hides data in the payloads of marked IP packets’ fragments. In the last method; packet fragmentation is required to use the bits of the fragment offset field in an intelligent way to hash the data before hiding it in the fragment’s payload.