TY - GEN A1 - Holz, Ralph A1 - Hiller, Jens A1 - Amann, Johanna A1 - Razaghpanah, Abbas A1 - Jost, Thomas A1 - Vallina-Rodriguez, Narseo A1 - Hohlfeld, Oliver T1 - Tracking the deployment of TLS 1.3 on the Web: A story of experimentation and centralization T2 - ACM SIGCOMM Computer Communication Review Y1 - 2020 U6 - https://doi.org/10.1145/3411740.3411742 SN - 0146-4833 VL - 50 IS - 3 ER - TY - GEN A1 - Hiller, Jens A1 - Amann, Johanna A1 - Hohlfeld, Oliver T1 - The Boon and Bane of Cross-Signing: Shedding Light on a Common Practice in Public Key Infrastructures T2 - CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020 N2 - 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. KW - Security and privacy KW - Network security Y1 - 2020 U6 - https://doi.org/10.1145/3372297.3423345 SP - 1289 EP - 1306 ER - TY - GEN A1 - Hiller, Jens A1 - Henze, Martin A1 - Zimmermann, Torsten A1 - Hohlfeld, Oliver A1 - Wehrle, Klaus T1 - The Case for Session Sharing: Relieving Clients from TLS Handshake Overheads T2 - 2019 IEEE 44th LCN Symposium on Emerging Topics in Networking (LCN Symposium), 14-17 Oct. 2019, Osnabrück, Germany N2 - In recent years, the amount of traffic protected with Transport Layer Security (TLS) has significantly increased and new protocols such as HTTP/2 and QUIC further foster this emerging trend. However, protecting traffic with TLS has significant impacts on network entities. While the restrictions for middleboxes have been extensively studied, addressing the impact of TLS on clients and servers has been mostly neglected so far. Especially mobile clients in emerging 5G and IoT deployments suffer from significantly increased latency, traffic, and energy overheads when protecting traffic with TLS. In this paper, we address this emerging topic by thoroughly analyzing the impact of TLS on clients and servers and derive opportunities for significantly decreasing latency of TLS communication and downsizing TLS management traffic, thereby also reducing TLSinduced server load. We propose a protocol compatible redesign of TLS session management to use these opportunities and showcase their potential based on mobile device traffic and mobile web-browsing traces. These show promising potentials for latency improvements by up to 25.8% and energy savings of up to 26.3%. KW - TLS Performance, Efficient Secure Communication, TLS Session Resumption, Network Security, Security and Privacy, Mobile Networking, 5G and IoT Y1 - 2019 UR - https://ieeexplore.ieee.org/document/9000667 SN - 978-1-7281-2561-9 SN - 978-1-7281-2562-6 U6 - https://doi.org/10.1109/LCNSymposium47956.2019.9000667 PB - IEEE ER -