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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2004.10.011 Byline: Yu-Yi Chen (a), Jinn-Ke Jan (b), Chin-Ling Chen (c) Abstract: All mobile phone subscribers must pay a subscription fee to enjoy the convenience of this technology. Subscribers pay for the actual time spent talking on the cellular phone. Generally, there are two kinds of billing. With prepaid service, the subscriber buys a prepaid card and pays for the cellular phone service in advance. As the subscriber uses airtime the cellular phone account is debited the appropriate amount of cellular phone service used. When the subscriber runs out of dollars in the cellular phone account, they can no longer call until the account is prepaid for additional cellular phone service or airtime. With postpaid service, cellular carriers bill customers based on how many minutes of airtime they use each month. When the customer places a call on an activated cellular phone, each minute the phone is connected is counted. Cellular carriers bill the customer on a monthly basis for the airtime used. There are some issues worth discussing such as fairness, non-repudiation, and non-usurpation. In this paper we propose a fair and secure mobile billing system. We introduce the "observer" concept to supervise billing to make it more objective and accepted by both cellular carriers and subscribers. The proposed scheme can detect illegal phone calls in real time and the subscriber cannot deny the deserved fees. Author Affiliation: (a) Department of International Business, Providence University, Taichung, Taiwan 433, ROC (b) Institute of Computer Science, National Chung Hsing University, Taichung, Taiwan 402, ROC (c) Institute of Applied Mathematics, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, Taiwan 402, ROC Article Note: (miscellaneous) Responsible Editor: J.Y.B. Lin

Two efficient authenticated encryption schemes with message linkages are proposed. One is a basic scheme, that it has the better performance in comparison with the all previously proposed schemes in terms of the communication and the computation costs. However, it has a property as same as the previously proposed schemes, that the message blocks can be recovered only after the entire signature blocks have been received. Therefore, the basic scheme is applicable to encrypt all-or-nothing flow. Thus, we improve the basic scheme and also propose a generalized scheme, which allows the receiver to recover the partial message blocks before receiving the entire signature blocks. That is, the receiver may perform the receiving and the recovering processes simultaneously. Therefore, the generalized scheme is applicable to message flows. The generalized scheme requires smaller bandwidth and computational time as compared to the previously proposed authenticated encryption schemes with message linkages for message flows. Keywords: Cryptography; Authenticated encryption; Message flows; Message linkage

The integration of communication protocols into transport systems is a much adored research area today. Much of seminal work has been reported on the topic of intelligent transportation systems (ITS) in the recent years. Many advanced techniques have been garnered to improve online communication and to promote the security, comfort, and efficiency of ITS. Of primary importance to the effective application of ITS is the communication protocol used. A fascinating development is that the yesterday's Global System for Mobile Communication protocol is being replaced by the Universal Mobile Telecommunication System protocol, which is the third-generation mobile technology. This article attempts to identify a suitable communication system for ITS applications. It is impracticable to substantially modify the original UMTS-IMS-AKA protocol which is in practice because it can disturb the operation of the current system, and thus we explore other possibilities through this research. We investigate a novel protocol to make the original UMTS-IMS-AKA protocol compliant with ITS as well as adaptable into the current UMTS protocol.

In 2000, Shieh et al. proposed two novel multisignature schemes (a serial multisignature scheme and a parallel multisignature scheme) that are suitable for authenticating the delegated access, because of its efficiency of computation and communication, message recovery, and no pre-determination of signers and their signing order. However, this article will show that the two schemes are vulnerable to the forgery attacks. Index Terms--Authentication, cryptography, multisignature.