@misc{HolzHillerAmannetal., author = {Holz, Ralph and Hiller, Jens and Amann, Johanna and Razaghpanah, Abbas and Jost, Thomas and Vallina-Rodriguez, Narseo and Hohlfeld, Oliver}, title = {Tracking the deployment of TLS 1.3 on the Web: A story of experimentation and centralization}, series = {ACM SIGCOMM Computer Communication Review}, volume = {50}, journal = {ACM SIGCOMM Computer Communication Review}, number = {3}, issn = {0146-4833}, doi = {10.1145/3411740.3411742}, pages = {12}, language = {en} } @misc{HillerAmannHohlfeld, author = {Hiller, Jens and Amann, Johanna and Hohlfeld, Oliver}, title = {The Boon and Bane of Cross-Signing: Shedding Light on a Common Practice in Public Key Infrastructures}, series = {CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020}, journal = {CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020}, doi = {10.1145/3372297.3423345}, pages = {1289 -- 1306}, abstract = {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.}, language = {en} }