Dr. Ralph Holz

Adjunct member of the Chair
Image a3de8b9d

Postal address

School of IT
University of Sydney
1 Cleveland St
Darlington NSW 2008

Visiting address

Building J12
Room 414


Current position

I am the Lecturer (Asst. Prof.) in Networks and Security at the School of IT at the University of Sydney and an Academic Visitor at the University of New South Wales. I also collaborate closely with Data61 (CSIRO), Australia's premier ICT innovation group.

As an adjunct member of this Chair, I continue to advise some topics. From time to time, I can offer Bachelor's/Master's theses in Australia in collaboration with TUM, aimed at outstanding students with an interest to broaden their horizon. Please contact me directly if you are interested - and also allow ample time for an application (at least 6 months).

There are also opportunities to do a PhD with me in Sydney - applications are competitive. PhDs may come with a scholarship and can be carried out in collaboration with Data61 (these are closer to industry and come with a top-up). If you wish to pursue research in Australia, please write me an email and allow enough time for an application (7+ months before the start date).

My current personal homepage is here.


My research interests revolve around network measurement and security, with a decidedly empirical approach. My current interests are:

  • Global-scale measurement of Internet service deployments and their security
  • Data-driven security mechanisms
  • Analysis of blockchain technology and its implications

My topic is real-world security: Security is achieved only by technology that its supports human users. No matter how brilliant the technology, if humans find it hard to operate, it will be insecure. Similarly, technology is always used in a context (at home, in finance, etc.) and this context is important in understanding how a technology must designed.

Supervised Theses


Author Title Type Advisors Year Links
Christian Korscheck Optimierung von virtuellen privaten Netzen mit Peer-2-Peer-Technologien Studienarbeit Dirk Haage, Ralph Holz
Jakob Bachhuber Confidential mail: improving email security with network measurements MA Ralph Holz 2016
Dario Banfi Endpoint-transparent multipath in Software Defined Networks MA Ralph Holz 2015
Max Liebkies Extension of a DNS scanner and conduction of large-scale DNS scans MA Johannes Naab, Ralph Holz 2014
Stefan König Scanning and Analysing the DNS for local and temporal Influences MA Johannes Naab, Ralph Holz 2014
Jan Seeger A scientific workbench with unified access to measurement data MA Ralph Holz, Johann Schlamp 2014
Nils Mäurer Efficient scans of large research networks BA Ralph Holz, Oliver Gasser 2014
Matthias Jaros Deployment and orchestration of network measurements using the PlanetLab testbed BA Ralph Holz, Oliver Gasser 2014
Omar Tarabei A pen-testing framework for the Munich Research Network IDP Ralph Holz 2013 Pdf
Johannes Naab Scannning and Evaluating DNS Deployments in the Internet MA Oliver Gasser, Ralph Holz, Johann Schlamp 2013
Franz Saller Understanding Certificate Revocation: OCSP, CRLs, and data sets MA Ralph Holz 2013 Pdf
Robert Kulzer Host profiling based on remote measurements Master thesis Ralph Holz 2012
Oliver Gasser Conducting large-scale active and passive measurements of SSH deployments MA Ralph Holz 2012
Leon Winter A scanner for privacy-violating techniques on the WWW IDP Ralph Holz 2012
Andrey Uzunov A library and proxy for SPDY IDP Ralph Holz 2012
Maximilian Szengel Spontaneous Private Networking - Governed by Security Policies Master thesis Ralph Holz, Christian Grothoff, Bart Polot, Heiko Niedermayer 2012 Pdf
Irfan Basha Privacy Crawler MA Ralph Holz 2012
Thomas Riedmaier Turning the Tables - Hunting the SSL/TLS Men-in-the-Middle Master thesis Ralph Holz, Heiko Niedermayer 2011 Pdf
Arne Wirtz Looking for SSH phishers, compromised hosts and weak keys Master thesis Ralph Holz, Marc Fouquet, Lothar Braun 2011 Pdf
Simon Zimmermann PercoPastry: routing around failures Bachelor thesis Ralph Holz, Nils Kammenhuber 2011
David Ellermann Protecting against JavaScript-based attacks with signatures Bachelor thesis Ralph Holz, Heiko Niedermayer, Phillip Fehre 2011
Simon Dieterle Rapping their knuckles - monitoring X.509 certificate revocation Bachelor thesis Ralph Holz, Nils Kammenhuber, Lothar Braun 2011 Pdf
Jan Seeger Conducting and Analysing Eclipse Attacks on the Kad P2P Network (aMule/eMule) Bachelor thesis Ralph Holz 2010 Pdf
Sven Wiebusch Entwicklung und Bewertung richtlinienbasierter Sicherheitskonzepte in spontanen virtuellen Netzen Diplomarbeit Ralph Holz, Heiko Niedermayer 2009
Rainer Boie Empirische Untersuchung von Angriffen auf strukturierte P2P-Netze Diplomarbeit Ralph Holz 2009
Alexander Ulrich Analyse und Visualisierung der Vertrauensbeziehungen in Web of Trust-Netzwerken Studienarbeit Ralph Holz 2009 Pdf
Rainer Boie Secure Node-ID Assignment in P2PSIP Networks Studienarbeit Ali Fessi, Ralph Holz 2008


2018-11-01 Quirin Scheitle, Oliver Gasser, Theodor Nolte, Johanna Amann, Lexi Brent, Georg Carle, Ralph Holz, Thomas C. Schmidt, Matthias Wählisch, “The Rise of Certificate Transparency and Its Implications on the Internet Ecosystem,” in Internet Measurement Conference (2018), Boston, USA, Nov. 2018, pp. 343–349. [Rawdata] [Arxiv] [DOI] [Bib]
2018-04-01 Quirin Scheitle, Taejoong Chung, Jens Hiller, Oliver Gasser, Johannes Naab, Roland van Rijswijk-Deij, Oliver Hohlfeld, Ralph Holz, Dave Choffnes, Alan Mislove, Georg Carle, “A First Look at Certification Authority Authorization (CAA),” ACM SIGCOMM Computer Communications Review (CCR), Apr. 2018. [Url] [Pdf] [Preprint] [Homepage] [Rawdata] [Bib]
2018-03-01 Oliver Gasser, Benjamin Hof, Max Helm, Maciej Korczynski, Ralph Holz, Georg Carle, “In Log We Trust: Revealing Poor Security Practices with Certificate Transparency Logs and Internet Measurements,” in Proceedings of the Passive and Active Measurement Conference (PAM 2018), Best Paper Award, Berlin, Germany, Mar. 2018. [Url] [Pdf] [Slides] [Sourcecode] [Rawdata] [Blog] [Bib]
2017-11-01 Johanna Amann*, Oliver Gasser*, Quirin Scheitle*, Lexi Brent, Georg Carle, Ralph Holz, “Mission Accomplished? HTTPS Security after DigiNotar,” in Proceedings of the Internet Measurement Conference (IMC 2017), IMC’17 Community Contribution Award, IRTF Applied Networking Research Prize (ANRP) 2018, London, UK, Nov. 2017. [Url] [Pdf] [Slides] [Sourcecode] [Rawdata] [Bib]
2016-06-01 Johann Schlamp, Ralph Holz, Quentin Jacquemart, Georg Carle, Ernst Biersack, “HEAP: Reliable Assessment of BGP Hijacking Attacks,” IEEE Journal on Selected Areas in Communications, Special Issue on Measuring and Troubleshooting the Internet: Algorithms, Tools and Applications; Volume 34 #6; ISSN: 0733-8716, pp. 1849–1861, Jun. 2016. [Bib]
2016-02-01 Ralph Holz, Johanna Amann, Olivier Mehani, Matthias Wachs, Mohamed Ali Kafaar, “TLS in the wild—An Internet-wide analysis of TLS-based protocols for electronic communication,” in Proc. Network and Distributed System Symposium (NDSS 2016), San Diego, CA, USA, Feb. 2016. [Pdf] [Bib]
2016-01-01 Dario Banfi, Olivier Mehani, Guillaume Jourjon, Lukas Schwaighofer, Ralph Holz, “Endpoint-transparent multipath transport with software-defined networks,” in 41st IEEE Conference on Local Computer Networks (LCN), 2016. [Pdf] [Bib]
2015-09-01 Olivier Mehani, Ralph Holz, Simone Ferlin, Roksana Boreli, “An Early Look at Multipath TCP Deployment in the Wild,” in Proc. 6th Int. Workshop on Hot Topics in Planet-Scale Measurement, Paris, France, Sep. 2015. [Pdf] [Bib]
2015-05-01 Yaron Sheffer, Ralph Holz, Peter Saint-Andre, “RFC 7525: Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS).” Best Current Practice (BCP 195). \urlhttps://tools.ietf.org/html/rfc7525, May-2015. [Bib]
2015-05-01 Len Bass, Ralph Holz, Paul Rimba, An Binh Tran, Liming Zhu, “Securing a deployment pipeline,” in Proc. 3rd Int. Workshop on Release Engineering, Florence, Italy, May 2015. [Bib]
2015-04-01 Johann Schlamp, Ralph Holz, Oliver Gasser, Andreas Korsten, Quentin Jacquemart, Georg Carle, Ernst W. Biersack, “Investigating the Nature of Routing Anomalies: Closing in on Subprefix Hijacking Attacks,” in Proc. 7th Int. Workshop on Traffic Monitoring and Analysis, Barcelona, Spain, Apr. 2015. [Pdf] [Bib]
2015-02-01 Yaron Sheffer, Ralph Holz, Peter Saint-Andre, “RFC 7457: Summarizing Known Attacks on Transport Layer Security (TLS) and Datagram TLS (DTLS).” Informational. \urlhttps://tools.ietf.org/html/rfc7457, Feb-2015. [Bib]
2014-05-01 Ralph Holz, “Empirical analysis of Public Key Infrastructures and investigation of improvements,” PhD thesis, Technische Universität München, May 2014. [Pdf] [Bib]
2014-05-01 Oliver Gasser, Ralph Holz, Georg Carle, “A deeper understanding of SSH: results from Internet-wide scans,” in Proc. 14th Network Operations and Management Symposium (NOMS), Krakow, Poland, May 2014. [Pdf] [Bib]
2012-09-01 Ralph Holz, Thomas Riedmaier, Nils Kammenhuber, Georg Carle, “X.509 Forensics: Detecting and Localising the SSL/TLS Men-in-the-middle,” in Proc. 17th European Symposium on Research in Computer Security (ESORICS 2012), Pisa, Italy, Sep. 2012, vol. 7459/2012, pp. 217–234. [Pdf] [Homepage] [Bib]
2011-11-01 Ralph Holz, Lothar Braun, Nils Kammenhuber, Georg Carle, “The SSL Landscape - A Thorough Analysis of the X.509 PKI Using Active and Passive Measurements,” in Proc. ACM/USENIX 11th Annual Internet Measurement Conference (IMC ’11), Berlin, Germany, Nov. 2011. [Pdf] [Homepage] [Bib]
2011-09-01 Alexander Ulrich, Ralph Holz, Peter Hauck, Georg Carle, “Investigating the OpenPGP Web of Trust,” in Proc. 16th European Symposium on Research in Computer Security (ESORICS 2011), Sep. 2011, vol. 6879/2011, pp. 489–507. [Pdf] [Homepage] [Bib]
2011-01-01 Holger Kinkelin, Ralph Holz, Heiko Niedermayer, Simon Mittelberger, Georg Carle, “On Using TPM for Secure Identities in Future Home Networks,” Future Internet, vol. 3, no. 1, pp. 1–13, 2011. [Pdf] [DOI] [Bib]
2010-10-29 Holger Kinkelin, Ralph Holz, Heiko Niedermayer, Georg Carle, “On Using TPM for Secure Identities in Future Networks (ext. abstract),” in Proceedings of Security in NGNs and the Future Internet Workshop, Sep. 2010. [Bib]
2010-08-01 Ali Fessi, Nathan Evans, Heiko Niedermayer, Ralph Holz, “Pr2-P2PSIP: Privacy Preserving P2P Signaling for VoIP and IM,” in Principles, Systems and Applications of IP Telecommunications (IPTComm), Munich, Aug. 2010. [Pdf] [Bib]
2010-06-01 Holger Kinkelin, Heiko Niedermayer, Ralph Holz, Georg Carle, “TPM-based Access Control for the Future Internet (ext. abstract),” in 5th GI/ITG KuVS Workshop on Future Internet, Stuttgart, Germany, Jun. 2010. [Bib]
2010-03-01 Dirk Haage, Ralph Holz, “Towards Measurement Consolidation for Overlay Optimization and Service Placement,” Praxis der Informationsverarbeitung und Kommunikation (PIK), vol. 10, pp. 12–15, Mar. 2010. [Bib]
2009-12-01 Ralph Holz, Christoph P. Mayer, Sebastian Mies, Heiko Niedermayer, Muhammad Adnan Tariq, “SpoVNet Security Task Force Report,” Universität Karlsruhe, Karlsruhe, Germany, Technical Report TM-2009-3, Dec. 2009. [Pdf] [Homepage] [Bib]
2009-11-01 Ralph Holz, Dirk Haage, “CLIO/UNISONO: Practical Distributed and Overlay-Wide Network Measurement (ext. abstract),” in 4th GI/ITG KuVS Workshop on The Future Internet and 2nd Workshop on Economic Traffic Management (ETM), Zürich, Switzerland, Nov. 2009. [Bib]
2009-11-01 Dirk Haage, Ralph Holz, “Optimization of Distributed Services with UNISONO (ext. abstract),” in GI/ITG KuVS Fachgespräch NGN Service Delivery Platforms & Service Overlay Networks, Berlin, Germany, Nov. 2009. [Bib]
2009-09-01 Heiko Niedermayer, Ralph Holz, Marc-Oliver Pahl, Georg Carle, “On Using Home Networks and Cloud Computing for a Future Internet of Things,” in Proc. Future Internet Symposium 2009 (FIS 2009), Berlin, Germany, Sep. 2009. [Bib]
2009-03-01 Dirk Haage, Ralph Holz, Heiko Niedermayer, Pavel Laskov, “CLIO – A Cross-Layer Information Service for Overlay Network Optimization,” in Kommunikation in Verteilten Systemen (KiVS) 2009, Kassel, Germany, Mar. 2009. [Pdf] [Homepage] [Bib]
2008-12-01 Oliver Waldhorst, Christian Blankenhorn, Dirk Haage, Ralph Holz, Gerald Koch, Boris Koldehofe, Fleming Lampi, Christoph Mayer, Sebastian Mies, “Spontaneous Virtual Networks: On the Road towards the Internet’s Next Generation,” it – Information Technology Special Issue on Next Generation Internet, vol. 50, no. 6, pp. 367–375, Dec. 2008. [Pdf] [Homepage] [Bib]
2008-04-01 Ralph Holz, Heiko Niedermayer, “A Protocol for Inter-Domain Authentication with a Trust-Rating Mechanism.,” in 8. Kryptotag der GI-Fachgruppe KRYPTO (Workshop). Technical Report WSI-2008-02. University of Tübingen, Apr. 2008. [Bib]
2008-01-01 Ralph Holz, Heiko Niedermayer, Peter Hauck, Georg Carle, “Trust-Rated Authentication for Domain-Structured Distributed Systems,” in Proc. 5th European PKI Workshop: Theory and Practice (EuroPKI 2008), Trondheim, Norway, 2008. [Pdf] [Bib]