WPKI中证书撤销验证的代理OCSP方案

在WPKI中,如何在无线终端设备中验证服务器证书是否撤销是一个复杂的问题。对此提出一种新的方案,称之为“代理OCSP方案”。它是对OCSP协议的改进,能够用较小的代价获得证书的实时状态。给出这种方案的详细设计,并和其他方案进行了比较。     

一种高效实用的证书验证机制的研究

在公钥基础设施当中,数字证书有可能在没有到期就要撤销它.PKI主要提供了两种证书撤销方法,就是周期性发布的证书撤销列表CRL和在线证书状态协议OCSP.详细地分析了CRL和OCSP两种证书撤销机制的优点和局限性,结合两者各自的优点,提出了一个高效实用的证书验证机制.给出了该机制的工作原理,并详细地介绍了的实现方法.     

证书撤销机制的分析与研究

数字证书是实现电子政务和电子商务中实体的信任及信任验证的关键元素.CA实际可能会根据不同的情况而导致证书的意外作废或撤销,那么应使要使用证书的用户尽可能获知最新的证书情况,这对于实现PKI系统的可信性至关重要.通过分析国内外通常采用的CRL和OCSP这两种基本的证书撤销、查询方法,总结了它们的优缺点以及在实际应用过程中遇到的难点.最后提出了相应的改进措施,使用户能及时获得最新的证书状况,为电子政务和电子商务提供更可靠的安全性.     

基于OCSP方式的证书撤销策略

阐述了在线证书状态协议(OCSP)方式的证书撤销机制的原理,针对单服务员模式建立了一个策略评估模型。该模型基于排队理论对系统机制进行了简化和抽象,通过该模型对OCSP方式的证书撤销策略进行评价,结合模型对影响系统的排队时间、网络带宽、验证速度等相关参数进行了讨论,分析了机制中的多服务员模型。     

基于LDAP目录服务的OCSP实现模型

提出一种基于LDAP目录服务的OCSP(Online Certificate Status Protocol)实现模型。新模型使用LDAP目录数据库存储OCSP响应器中的证书撤销数据,同时记录实体间证书验证关系;响应器为服务的实体提前收集验证证书的撤销信息,提前准备签名,部分减少了OCSP响应器对撤销数据库的搜索范围和签名时间。实验结果表明,这一方法降低了OCSP平均响应时间,提高了响应器的性能。     

基于单向哈希函数的证书撤销机制

证书撤销是公钥基础设施PKI(Public Key Infrastructure)研究和应用的难点问题.首先讨论了当前应用最广泛的两类证书撤销机制:证书撤销列表CRL(Certificate Revocation List)和在线证书状态协议OCSP(0nline Certificate Status Protoco1),剖析了这两种机制各自存在的不足.在此基础上,提出了一种基于单向哈希函数的证书撤销机制.     

无线PKI中证书状态查询机制研究与实现

无线PKI技术在移动电子商务中扮演着重要角色,而证书状态查询机制是其关键部件.对无线PKI中的3种常见的证书状态查询机制进行了分析和比较;OCSP协议能够提供实时的证书状态查询服务,但由于无线PKI的特殊限制,并不能直接应用于无线PKI环境中.在充分考虑无线PKI特殊的限制条件基础上,给出了一种基于OCSP协议的适合无线PKI环境的证书状态查询设计方案;详细描述了该设计在具体实现中需要特别注意的几项关键技术,以提高系统的性能和安全性.     

一种可撤销的KP-ABE方案

提出了一个支持私钥撤销的KP-ABE(Key Policy Attribute Based Encryption)方案, 该方案以直接撤销模式对用户进行撤销, 能够在不更新系统公钥和任何一个用户的私钥的情况下完成对用户的撤销, 更新代价较小.同时该方案基于访问树实现与Attrapadung 等人基于LSSS(Linear Secret Sharing Schemes)的支持用户撤销的KP-ABE 方案相比, 构造更为简单. 该方案的安全性可以规约到标准模型下的判定性q-BDHE(q-Bilinear Diffie-Hellman Exponent)假设.     

基于单向散列链的公钥证书撤销机制

证书撤销是公钥基础设施（PKI，Public Key Infrastructure）研究和应用的难点问题．本文首先讨论了当前应用最广泛的两类证书撤销机制一证书撤销列表（CRL，Certificate Revocation List）和在线证书状态罅议（OCSP，Online Certificate Status Protocol），剖析了这两种机制各自存在自的不足．在此基础上，提出了一种基于单向散列链的证书撤销机制．     

一种基于分段的CRL改进方案

分析了有序顺序表和二叉排序树表的证书撤销列表方案的不足,提出了一种基于分段的证书撤销列表CRL（Certificate Revocation List）改进方案,给出了按撤销证书到期的时间间隔的分段策略,并对CRL结构进行了改进。通过分析表明,缩短了证书用户查找撤销证书的平均搜索长度,在CRL更新时,不但减少了其它已撤销证书的移动次数,而且还减少了CA对CRL重新签名的计算量。     

基于短消息的数字证书状态发布系统的研究

在任何一个基于公钥基础设施的安全应用系统中,数字证书的验证对保证系统的安全具有至关重要的作用。简要描述了因特网中通过OCSP进行在线证书状态查询的方法,说明了目前加密手机无法像因特网一样进行在线数字证书状态查询的原因,提出了一种基于短消息的数字证书撤销状态发布方案,有效地解决了无线环境中的数字证书状态验证问题,提高了加密手机的安全水平。     

无线环境下一种新的证书状态查询方案

分析有线环境现有证书状态查询方案的基础上,提出了一种对传统的 O C S P进行了改进的方案-用户端部分缓存的ocsp方案,并将其与其他证书状态查询方案进行了比较。该方案借鉴了哈希链的思想,具有很高的安全性,可以有效减少用户端及服务器端的运算量,降低带宽负荷,适合用作无线环境下的证书状态查询方案。     

Tracking adoption of revocation and cryptographic features in X.509 certificates

SSL certificates hold immense importance when it comes to the security of the WebPKI. The trust in these certificates is driven by the strength of their cryptographic attributes and the presence of revocation features. In this paper, we perform a historical measurement study of cryptographic strength and the adoption of revocation mechanisms in the X.509 SSL certificates. In particular, it provides a real-world picture of the adoption of new certificate features and pushing new changes to the WebPKI ecosystem. We analyze the features like Online Certificate Status Protocol (OCSP) Stapling, RSA public key collisions, and the strength of certificate serial numbers. We observe the improvement in the adoption and reliability of these features for 2011–2020. Our analysis helps in identifying weaknesses and negligence in certificate issuance practices of Certificate Authorities such as lack of revocation, weak serial numbers, and issuance of the same public key across different certificates for different entities on the web known as the public key collision problem. Our results show that there is an overall increase of up to 97% in the adoption of OCSP-Stapling and OCSP extensions. Along with this, there are also significant improvements in the certificate serial number length with the top 6 CAs in our dataset issuing the majority of certificates with serial byte count greater than 30. We also discovered 803 public key collision sets in our dataset. To distinguish public key collisions, we provide a working criterion to distinguish permissible, safe collisions from unsafe, risky ones. Analysis of these features holds immense importance as weakness in any of these features could allow an adversary to forge certificate(s) and conduct several attacks examples of which include Flame malware, breach of the DigiNotar and Comodo certificate authorities.

     

A robust and flexible digital rights management system for home networks

A robust and flexible Digital Rights Management system for home networks is presented. In the proposed system, the central authority delegates its authorization right to the local manager in a home network by issuing a proxy certificate, and the local manager flexibly controls the access rights of home devices on digital contents with its proxy certificate. Furthermore, the proposed system provides a temporary accessing facility for external devices and achieves strong privacy for home devices. For the validation of delegated rights and the revocation of compromised local managers, a hybrid mechanism combining OCSP validation and periodic renewal of proxy certificates is also presented.     

A revocable ID-based authenticated group key exchange protocol with resistant to malicious participants

Authenticated group key exchange (AGKE) protocol provides secure group communications for participants in cooperative and distributed applications over open network environments such as the Internet and wireless networks. In the past, a number of AGKE protocols based on the identity (ID)-based public key system (IDPKS) have been proposed, called ID-AGKE protocols. In the IDPKS system, users’ identities are viewed as the public keys to eliminate certificate management of the traditional certificate-based public key system. Nevertheless, any certificate-based public key systems or IDPKS systems must provide a revocation mechanism to revoke misbehaving/compromised users from the public key systems. However, there was little work on studying the revocation problem of the IDPKS system. Quite recently, Tseng and Tsai presented a new ID-based encryption scheme and its associated revocation mechanism to solve the revocation problem efficiently, called revocable ID-based public key system (R-IDPKS). In this paper, we follow Tseng and Tsai’s R-IDPKS system to propose the first revocable ID-AGKE (RID-AGKE) protocol. Security analysis is made to demonstrate that the proposed RID-AGKE protocol is a provably secure AGKE protocol and can resist malicious participants. As compared to the recently proposed ID-AGKE protocols, the proposed RID-AGKE protocol is provably secure and has better performance while providing an efficient revocation mechanism.