Computer Laboratory

Khaled Baqer

Khaled Baqer

PhD student (Security Group, Computer Laboratory), supervised by Professor Ross Anderson. [2014 - 2018]

My thesis was published in November 2018: Baqer, K. (2018). Resilient payment systems (Doctoral thesis). and it's also available as technical report 929 published by the Lab.

SHA256(kabhb2-thesis.pdf)= 95710994405b93b6710e0373677302a63c06829d385cfc6215f74cd3c79889fa

My research interests include payment systems security (cryptocurrencies, mobile payment systems, EMV (Chip-and-PIN) payment protocol), and anonymous communication (including censorship-circumvention tools).


  • Reconciling Multiple Objectives –- Politics or Markets? (International Workshop on Security Protocols 2017, SPW25). [PDF] [Blog].
    This paper discusses the way in which protocols at different levels in the stack evolve on different timescales, and how we can use ideas from institutional economics to understand this.

  • DigiTally: offline payments [Project page]
    DigiTally is an overlay payment scheme for use on mobile phones, whose goals are to extend mobile phone payments to areas with poor connectivity and reduce transaction fees. DigiTally enables two people to do a payment transaction by simply copying short strings of numbers between their phones. This doesn't need either smartphones or a network connection. Either phone can upload the transaction later, once it gets a network connection.

    • DigiTally: Piloting Offline Payments for Phones (13th Symposium on Usable Privacy and Security, SOUPS 2017) [PDF] [Slides] [Blog]
    • SMAPs: Short Message Authentication Protocols (International Workshop on Security Protocols 2016, SPW24) [PDF]
    • SMAPs: Short Message Authentication Protocols (Transcript of discussion) [PDF]
  • Stressing Out: Bitcoin "Stress Testing" (3rd Workshop on Bitcoin and Blockchain Research) [PDF] [Slides]
    We present an empirical study of the July 2015 spam campaign (a "stress test") that resulted in a DoS attack on Bitcoin. The goal of our investigation being to understand the methods spammers used and impact on Bitcoin users. We use a clustering method to group transactions and show varying patterns, and we analyse the security economics of the spam campaign.
  • Do You Believe in Tinker Bell? The Social Externalities of Trust (International Workshop on Security Protocols 2015, SPW23) [PDF] [Blog]
    We explore how we can crowdsource trust. Just as a religion's power comes from its faithful rather than from the government, so also a trust service's power should derive from the users who trust it, rather than from the state or from a CA that's too big to fail.


  • Can we redesign mobile payments to deal with poor networks and cut transaction fees? public lecture given with Ross Anderson at Strathmore University (Nairobi, Kenya), 29 August 2016. [Slides]
  • DigiTally: offline payments at Technology for the Bottom Billion Workshop, 10th June 2016, organised by Centre for Global Equality and Centre for Research in the Arts, Social Sciences and Humanities. [Slides]
  • Cryptocurrencies: challenges and caveats at the Alan Turning Institute (ATI) workshop on "Data science for the digital economy: Digital currencies and peer-to-peer economics" which was held at the British Library on 10th December 2015. [Slides]

Contact Details

Khaled Baqer


PGP key [expires: 2019-07-10]
CB07 01A5 183A 5D64 682D 70A0 1F1A 6F5F ECEF 30D4

University of Cambridge, Computer Laboratory
15 JJ Thomson Avenue
Cambridge CB3 0FD
United Kingdom

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