Content Distribution Networks (CDNs) are highly advanced architectures for networks on the Internet, providing low latency, scalability, fault tolerance, and load balancing. One of the most important issues to realize these advantages of CDNs is dynamic content allocation to deal with temporal load fluctuation, which provides mirroring of content files in order to distribute user accesses. Since user accesses for content files change over time, the content files need to be reallocated appropriately. In this paper, we propose a cost-effective content migration method called the Step-by-Step (SxS) Migration Algorithm for CDNs, which can dynamically relocate content files while reducing transmission cost. We show that our method maintains sufficient performance while reducing cost in comparison to the conventional shortest-path migration method. Furthermore, we present six life cycle models of content to consider realistic traffic patterns in our simulation experiments. Finally, we evaluate the effectiveness of our SxS Migration Algorithm for dynamic content reconfiguration across time.

A multi-application smart card system consists of an issuer, service vendors and cardholders, where cardholders are recipients of smart cards (from the issuer) to be used in connection with applications offered by service vendors. Authentic post-issuance program modification is necessary for a multi-application smart card system because applications in the system are realized after the issuance of a smart card. In this paper, we propose a system where only authentic modification is possible. In the proposed system, the smart card issuer stores a unique long bitstring called PID in a smart card. The smart card is then given to the cardholder. A unique substring of the PID (subPID) is shared between the cardholder and a corresponding service vendor. Another subPID is shared between the issuer and the cardholder. During program modification, a protocol using the subPIDs, a one-way hash function and a pseudorandom number generator function verifies the identity of the parties and the authenticity of the program.