论文标题
交叉签名的福音和祸根：阐明公共密钥基础设施中的共同做法
The Boon and Bane of Cross-Signing: Shedding Light on a Common Practice in Public Key Infrastructures
论文作者
论文摘要
公共密钥基础架构（PKIS）及其受信任的证书机构（CAS）为Internet提供了信任骨干：CAS标志证书，证明了服务器，应用程序或用户的身份。要受到操作系统和浏览器的信任，CA必须经历冗长且昂贵的验证过程。另外，值得信赖的CA可以跨越其他CA，以扩大对他们的信任。在本文中，我们系统地分析了Web PKI中交叉签名的当前和过去状态。我们的数据集（源自被动TLS监视器和公共CT日志）涵盖了7年以上的2.25亿张证书，并拥有93亿个信任路径。我们表现出交叉签名的好处和风险。我们讨论撤销可信赖的CA证书的困难，令人担忧的交叉签名可能会导致有效的信任路径在撤销后留下；非浏览器软件的一个问题，通常盲目信任所有CA证书并忽略吊销。但是，交叉签名还可以通过提供向后兼容性来快速进行新CAS的快速引导，例如，让我们加密并实现非破坏性的用户体验。在本文中，我们提出了新的规则和指导，以交叉签名，以保持其积极的潜力，同时减轻风险。
Public Key Infrastructures (PKIs) with their trusted Certificate Authorities (CAs) provide the trust backbone for the Internet: CAs sign certificates which prove the identity of servers, applications, or users. To be trusted by operating systems and browsers, a CA has to undergo lengthy and costly validation processes. Alternatively, trusted CAs can cross-sign other CAs to extend their trust to them. In this paper, we systematically analyze the present and past state of cross-signing in the Web PKI. Our dataset (derived from passive TLS monitors and public CT logs) encompasses more than 7 years and 225 million certificates with 9.3 billion trust paths. We show benefits and risks of cross-signing. We discuss the difficulty of revoking trusted CA certificates where, worrisome, cross-signing can result in valid trust paths to remain after revocation; a problem for non-browser software that often blindly trusts all CA certificates and ignores revocations. However, cross-signing also enables fast bootstrapping of new CAs, e.g., Let's Encrypt, and achieves a non-disruptive user experience by providing backward compatibility. In this paper, we propose new rules and guidance for cross-signing to preserve its positive potential while mitigating its risks.
