Optimally Efficient Accountable Time-Stamping

  • Ahto Buldas
  • Helger Lipmaa
  • Berry Schoenmakers
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1751)


Efficient secure time-stamping schemes employ a 2-level approach in which the time-stamping service operates in rounds. We say that a time-stamping service is accountable if if it makes the TSA and other authorities accountable for their actions by enabling a principal to detect and later prove to a judge any frauds, including attempts to reorder time-stamps from the same round. We investigate the paradigm of time-stamping services based on simply connected graphs, and propose a simple, yet optimal, accountable time-stamping service, using what we call threaded tree schemes. We improve upon the previously best scheme by Buldas and Laud by reducing the size of a time stamp by a factor of about 3.786 and show that our construction is optimal in a strict sense. The new protocols also increase the trustworthiness of the publication process, which takes place at the end of each round.


Hash Function Publication Authority Time Stamp Black Vertex Digital Document 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Ahto Buldas
    • 1
  • Helger Lipmaa
    • 1
  • Berry Schoenmakers
    • 2
  1. 1.Küberneetika ASTallinnEstonia
  2. 2.Dept. of Mathematics and Computing ScienceEindhoven University of TechnologyEindhovenThe Netherlands

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