Realization of Secure and Practical Anonymous Communication System

在本研究中，我们开发了一个新的匿名通信系统Bifrost，以提高安全性和实用性的低延迟匿名通信系统的多个步骤和多级中继。Bifrost可以实现提高匿名性和减少多次重复的成本，并成功地提高了安全性和实用性。此外，我们提出了一种新的方法，应用基于身份的加密匿名通信系统，并成功地从他们删除目录服务器。因此，消除了目录服务器在匿名性和可伸缩性方面的下降，并提高了实用性。然而，我们不能提出一个新的方法来撤销匿名的发件人滥用匿名。我们的系统只是使用现有的撤销方法。

In this research, we developed a novel anonymous communication system Bifrost to improve safety and practicality of low-latency anonymous communication systems with multiple-encryptions and multistage-relay. Bifrost can realize improving anonymity and reducing costs of multiple-encryptions and succeed in improving safety and practicality. Moreover, we proposed a new method applying ID-based encryption to anonymous communication systems and succeeded in removing directory servers from them. Therefore a decline in anonymity and scalability by directory servers is removed and practicality is improved. However we cannot present a novel method revoking anonymity of a sender when it abused anonymity. Our system just uses an existing revoking method.