The Transport Layer Security (TLS) protocol constitutes the key building block for today's Internet security and is, for example, used for encrypted web connections using the HTTPS protocol. However, from its first version in 1994 until today, researchers and practitioners keep discovering TLS deficiencies undermining the protocol's security on a regular basis. While the academic community has applied intense scrutiny to the TLS/X.509 ecosystem, much of such work depends on access to difficult to acquire representative data on the protocol's deployment and usage. This project leverages an already operating large-scale passive TLS traffic measurement effort that has been continuously collecting TLS information from live Internet uplinks of 8 large research institutions with about 390,000 users total. The current data set contains more than 100 billion observed TLS connections with more than 100 million unique certificates. This project expands the collection effort and uses both historic and new data to perform studies of current TLS ecosystem trends as well as what-if analyses of future developments. The new measurements will address different parts of the TLS ecosystem, including studying the impact of certificate revocation, non-HTTPS deployments of TLS, and applications masquerading as TLS without actually speaking it. Furthermore, leveraging historic data, the project examines trends in TLS usage and deployment like the evolution of TLS software, session resumption, and virtual hosting. Finally, the project combines historic and new measurements to drive a series of what-if analyses predicting the impact of upcoming and proposed ecosystem changes like OCSP stapling for certificate revocation and Google's Certificate transparency. In addition to these measurement efforts, the project offers a community service that makes the data collection accessible to researchers and practitioners by allowing them to run their own analyses on the data set using a mediation process
TWC: TTP Option: Small: Understanding the State of TLS Using Large-scale Passive Measurements