Kiyohiko Ishikawa

Churn-resistant method for DHT-based content delivery systems

This paper describes a churn-resistant method for distributed hash table-based content delivery systems. We propose two algorithms; one involves multiple nodes synchronizing content indexes, the other involves leaving nodes transferring content indexes to joining nodes. Our proposed method was evaluated by a simulation estimated in a high churn environment. As a result, our method improved the sustainability of content indexes against churn without increasing network traffic.

New File System with Conditional Access System for Removable Media

Digital broadcasting has already been operational in Japan for years. All content and copyrights are protected by conditional access system (CAS). The next new services will be launched in 2007. This is broadcasting based on home servers. Broadcasting of digital content requires access to be controlled. A Secure File System (SFS) was developed to control access with a file system layer. This article describes the SFS, which is an excellent file system to manage security. The SFS commands content to be stored in a personal digital recorder (PDR) and removable media following a newly defined security robustness range. SFS is possible to use with other security application layers presently available. That is, SFS does not conflict with any present security systems with application layers. The data transfer rates with SFS are 10 % lower. These are sufficient to read/write digital broadcasting MPEG2 TS of about 20 Mbps. They were obtained at 10.7Mbyte/sec using an optical disk drive. Index Terms—Digital broadcasting, Home server, PDR, UDF, File system, Removable media