Research Based On TCP/IP Protocol Suits

The development of information,multimedia and network technology brings along digital era,but many problems ensue from the prevalence of digital technology and information.How to guarantee the transmission of the network data has been a main subject in information security.Traditional methods encrypted and disordered the information,then encapsulated it into the data field of TCP/IP datagrams. However,the effect was not so ideal.So,effective protection and successful transmission has always been an urgent problem.My research of covert channel mechanism is based on covert channel theory and steganography.This thesis investigates the existence of covert channels in computer networks by analyzing the transport and the Internet layers of the TCP/IP protocol suite and showes how to transfer data secretly in covert channel.Steganography is an important subdiscipline of information hiding.With steganography technoly,we can transfer data in covert channel more secretly and make covert channel more difficult to detect.Two approaches for buliding covert channel with steganography are identified in the thesis:1. steganography in ToS based on QoS security mechanismThe article proposes a new steganography in the ToS domain in the IP packet. The method makes use of the ID value of the IP packets to record the original packets sequence,and modifies the first three bits, which indicate the IP PRI, of ToS. Then, the modified IP PRI is utilized to rearrange the the packets sequence, and thus complete the information hiding without imposing any influence on the statistics, content and sending order of the IP packets.Combining with the ordering menthod,security and the capacity was greatly enhanced.Meanwhile,prescambled with FSA, covert information can be communicated with high security.2. steganography in IPID based on PPWLCMCommon methods make use the bugs and unused fields of TCP/IP protocol and secret information is embedded into the header of TCP/IP datagrams. However, obvious mark can be calculated by statistical research.The system PPWLCM (piece- parametered wise linear chaotic map)can adjust the piece parameter dynamicly according to the demand of calculation precision and complexity.Then,information is embedded into the high 8 bits in IPIDs.The experiments show a more approaching statistical feature to the original data.