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

  • Oliver Gasser
  • Benjamin Hof
  • Max Helm
  • Maciej Korczynski
  • Ralph Holz
  • Georg Carle
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10771)


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.


TLS Certificate Transparency Baseline Requirements 



We thank Emily Stark from Google for the valuable insights into Chrome’s current state of CT over DNS. The authors thank the contributors of data to Farsight Security’s DNSDB. We thank the anonymous reviewers and our shepherd Steve Uhlig for their valuable feedback. This work was partially funded by the German Federal Ministry of Education and Research under project X-Check, grant 16KIS0530, and project DecADe, grant 16KIS0538.


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Oliver Gasser
    • 1
  • Benjamin Hof
    • 1
  • Max Helm
    • 1
  • Maciej Korczynski
    • 2
    • 3
  • Ralph Holz
    • 4
  • Georg Carle
    • 1
  1. 1.Technical University of MunichMunichGermany
  2. 2.Grenoble Alps UniversityGrenobleFrance
  3. 3.Delft University of TechnologyDelftNetherlands
  4. 4.The University of SydneySydneyAustralia

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