In Log We Trust: Revealing Poor Security Practices with Certificate Transparency Logs and Internet Measurements


In recent years, multiple security incidents involving Certificate Authority (CA) misconduct demonstrated the need for strengthened certificate issuance processes. Certificate Transparency (CT) logs make the issuance publicly traceable and auditable. In this paper, we leverage the information in CT logs to analyze if certificates adhere to the industry’s Baseline Requirements. We find 907 k certificates in violation of Baseline Requirements, which we pinpoint to issuing CAs. Using data from active measurements we compare certificate deployment to logged certificates, identify non-HTTPS certificates in logs, evaluate CT-specific HTTP headers, and augment IP address hitlists using data from CT logs. Moreover, we conduct passive and active measurements to carry out a first analysis of CT’s gossiping and pollination approaches, finding low deployment. We encourage the reproducibility of network measurement research by publishing data from active scans, measurement programs, and analysis tools.

Proc. Passive and Active Measurements Conference (PAM)