交叉签名的利弊：揭示公钥加密结构中的一种常见做法
The Boon and Bane of Cross-Signing: Shedding Light on a Common Practice in Public Key Infrastructures
摘要：
公钥体系结构（PKI）及其受信任的证书颁发机构（CA）为Internet提供了信任基础：CA签署证明服务器、应用程序或用户身份的证书。为了得到操作系统和浏览器的信任，CA必须经历漫长而昂贵的验证过程。或者，受信任的CA可以交叉签名其他CA，以扩展对它们的信任。本文系统地分析了Web PKI中交叉签名的现状和发展趋势。我们的数据集（来自被动TLS监视器和公共CT日志）包含超过7年的2.25亿个证书和93亿个信任路径。我们展示了交叉签名的好处和风险。我们讨论了撤销可信CA证书的困难，令人担忧的是，交叉签名可能导致有效的信任路径在撤销后仍然存在;对于非浏览器软件来说，这是一个经常盲目信任所有CA证书并忽略验证的问题。然而，交叉签名还使得能够快速引导新CA，例如，Let's Encrypt，并通过提供向后兼容性实现无中断的用户体验。在本文中，我们提出了交叉签名的新规则和指导，以保持其积极的潜力，同时降低其风险。
英文摘要：
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.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
