Realization of Secure and Practical Anonymous Communication System

在本研究中，我们开发了一种新的匿名通信系统BiFrost，以提高多重加密和多级中继的低延迟匿名通信系统的安全性和实用性。BiFrost可以实现提高匿名性和降低多重加密的成本，成功地提高了安全性和实用性。此外，我们还提出了一种将基于身份的加密应用于匿名通信系统的新方法，并成功地将目录服务器从匿名通信系统中移除。因此，消除了目录服务器在匿名性和可伸缩性方面的下降，提高了实用性。然而，我们不能提出一种新的方法来撤销滥用匿名性的发送者的匿名性。我们的系统只是使用了现有的撤销方法。

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.