On the Theory and Practice of Personal Digital Signatures

  • Authors:
  • Ivan Damgård;Gert Læssøe Mikkelsen

  • Affiliations:
  • Depertment of Computer Science, Aarhus University,;Depertment of Computer Science, Aarhus University,

  • Venue:
  • Irvine Proceedings of the 12th International Conference on Practice and Theory in Public Key Cryptography: PKC '09
  • Year:
  • 2009

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Abstract

We take a step towards a more realistic modeling of personal digital signatures, where a human user, his mobile equipment, his PC and a server are all considered as independent players in the protocol, and where only the human user is assumed incorruptible. We then propose a protocol for issuing digital signatures on behalf of the user. This protocol is proactively UC-secure assuming at most one player is corrupted in every operational phase. In more practical terms, this means that one can securely sign using terminals (PC's) that are not necessarily trusted, as long as the mobile unit and the PC are not both corrupted at the same time. In other words, our solution cannot be broken by phising or key-logging via the PC. The protocol allows for mobile units with very small computing power by securely outsourcing computation to the PC and also allows usage of any PC that can communicate properly. Finally, we report on the results of a prototype implementation of our solution.