Theory of Distributed Cryptography and its application to Electronic Commerce Systems

公钥基础设施（PKI）是支持网络上安全的电子商务和数字通信的重要技术之一。已经提出了许多PKI信任模型，并广泛用于各种目的。我们考虑了两种信任模型：单个CA模型和从属层次模型。一个证书颁发机构（CA）颁发所有证书的信任模型是最简单的模型。我们称之为“单个CA模型”。在该模型中，认证路径的构建和验证过程非常简单，但存在CA密钥暴露率高的危险。从属层次模型缓解了这个问题。由于这个原因，从属层次模型在现实世界中非常流行。在本研究中，我们讨论了这两种模型的优缺点，并通过使用前向安全数字签名方案提出了证书路径比从属层次模型短的PKI信任模型。

A Public Key Infrastructure (PKI) is the one of the important techniques to support secure E-commerce and digital communication on networks. Many PKI trust models have been proposed and are widely used for various purposes.We consider two trust models: A Single CA model and A Subordinated Hierarchical model. The trust model that one Certification Authority (CA) issues all certificates is the simplest one. We call it "A Single CA model". In this model, construction and validation processes of certification path are very simple, however it is attended with danger of the high ratio of exposure CA's secret key. The subordinated hierarchical model mitigated this problem. For this reason, a subordinated hierarchical model is very popular in the real world. In this research, we discuss the advantages and disadvantages of these two models and suggest the PKI trust model that certificate path is shorter than one of a subordinated hierarchical model by using the forward-secure digital signature scheme.