Knowledge-Binding Commitments with Applications in Time-Stamping

Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4450)


We prove in a non-black-box way that every bounded list and set commitment scheme is knowledge-binding. This is a new and rather strong security condition, which makes the security definitions for time-stamping much more natural compared to the previous definitions, which assume unpredictability of adversaries. As a direct consequence, list and set commitment schemes with partial opening property are sufficient for secure time-stamping if the number of elements has an explicit upper bound N. On the other hand, white-box reductions are in a sense strictly weaker than black-box reductions. Therefore, we also extend and generalize the previously known reductions. The corresponding new reductions are \(\Theta(\sqrt{N})\) times more efficient, which is important for global-scale time-stamping schemes where N is very large.


Hash Function Commitment Scheme Coin Toss Security Guarantee Random Coin 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer Berlin Heidelberg 2007

Authors and Affiliations

  1. 1.Cybernetica AS, Akadeemia tee 21, 12618 TallinnEstonia
  2. 2.Tallinn University of Technology, Raja 15, 12618 TallinnEstonia
  3. 3.University of Tartu, Liivi 2, 50409 TartuEstonia
  4. 4.Helsinki University of Technology, Laboratory for Theoretical Computer Science, P.O.Box 5400, FI-02015 TKKFinland

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