Mobile Communication Authentication System Based On Dual-Watermark

With the rapid development of the network technology and the third generation mobile communication technology, how to ensure the security of3G network and business information has became an important topic. The authentication technology can provide the guarantee of credibility for the identity, content and process between the communicating parties, so it is widely used in network service system which takes the multimedia information as the main way of communication. The authentication effectively guarantees that the network resources cannot be used by unauthorized users, the user data cannot be illegally stolen and modified and the signaling cannot be eavesdropped and tampered.This thesis is devoted to studying the mobile communication authentication system based on dual-watermark after analyzing and discussing the limitation of traditional authentication system based on digital signature. In the new authentication system, a semi-fragile watermark and a robust watermark are embedded together at the same time. Using the semi-fragile watermark to authenticate the authenticity and integrity of communication content and using the robust watermark to authenticate the user’s identity and permission. The major works involved are as follows:(1) Producing the needed semi-fragile watermark by extracting the edge texture characteristic of carrier image. On one hand, the semi-fragile watermark is robust against conventional signal processing of the wireless communication but just fragile in the malicious modification. On the other hand, because the watermark is produced by extracting the edge texture characteristic, we can localize tampering by the extracted the watermark.(2) According to analyzing the advantages of the spread spectrum technology in wireless communication, such as its security, anti-noise and anti-interference performance, this thesis chooses the digital watermarking technology based on the spread spectrum to realize the certification of the user identity and authority. Experiment shows that the algorithm is robust against noise attacks but is weak in the malicious modification. The authentication effect of this communication system is not fallen well short of its goals.(3) According to analyzing the shortages of the watermark based on direct sequence spread spectrum technology, the authentication technology has been improved by using a new algorithm which is based on OFDM and combines spread spectrum watermarking technique with OFDM wireless transmission technology. The spread spectrum watermark is embedded in the QPSK mapping sequence of the carrier signal. Then transfer the new watermark including sequence in OFDM. This watermark has good robustness, whether noise or malicious modification will not make it affected.Experiments show that the mobile communication authentication system which combines the semi-fragile watermark based on image edge detection with the robust watermark based on OFDM and Spread spectrum technology has a good effect on authentication of the communication content and user identity.