A simple authentication technique for use in the global mobility network (GLOMONET) is proposed. This technique is based on the concept of distributed security management, i.e., the original security manager administrates the original authentication key (long-term secret key) acquired when a user makes a contract with his home network, while a temporary security manager is generated for a roaming user in the visited network that provides roaming services. The temporary security manager will take the place of the original security manager when the roaming user stays in the service area of the visited network. In the proposed authentication protocol for the regular communication phase, the procedures of the original security manager and the temporary security manager are the same except for introducing different parameters. Furthermore, the proposed technique not only reduces the number of transmissions during the authentication phase, but it also can decrease the complexity of mobile equipment. The idea behind the proposed technique is to introduce a simple mechanism which is called "self-encryption". We also suggest that this mechanism can be easily adopted as the authentication function for the secure teleconference service.

This paper presents a copyright owner detection technique for images and graphics. A digital time-stamped signature for this copyright identification technique is also introduced in this work. The secret key, used to compute the watermark, is generated from the extracted features of the host images in the proposed scheme. The proposed algorithm enables the successful revealing of watermarks under several attacks, such as filtering, lossy compression, cropping, rotating, and so on. In particular, our method is not only suitable for ordinary natural images, but can also be applied to cartoon graphics. Most importantly, the proposed scheme can be applied to the media in which distortion is not allowable, such as medical images, source code of programs, and so on.

In practice, we usually require two cryptosystems, an asymmetric one and a symmetric one, to encrypt a large confidential message. The asymmetric cryptosystem is used to deliver secret key SK, while the symmetric cryptosystem is used to encrypt a large confidential message with the secret key SK. In this article, we propose a simple cryptosystem which allows a large confidential message to be encrypted efficiently. Our scheme is based on the Diffie-Hellman distribution scheme, together with the ElGamal cryptosystem.

A technique for proving copyright ownership of images is proposed. We use the moment-preserving to represent the characteristics of images. The secret key for copyright detection is generated from the image's feature and the owner's watermark/trademark. This strategy for a watermarking system is wholly different from traditional work. Furthermore, a voting approach is used to improve the correctness of the computed watermarks. Experimental results show that our method survive can against several attacks. These attacks are from image processing algorithms, such as filtering, lossy compression, rotation and so on. In particular the proposed scheme is not only applicable to ordinary natural images but also to cartoon graphics.