Generic on-line/off-line threshold signatures

  • Authors:

  • Chris Crutchfield;David Molnar;David Turner;David Wagner

  • Affiliations:

  • University of California, Berkeley;University of California, Berkeley;University of California, Berkeley;University of California, Berkeley

  • Venue:
  • PKC'06 Proceedings of the 9th international conference on Theory and Practice of Public-Key Cryptography
  • Year:
  • 2006

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Abstract

We present generic on-line/off-line threshold signatures, in which the bulk of signature computation can take place “off-line” during lulls in service requests [6]. Such precomputation can help systems using threshold signatures quickly respond to requests. For example, tests of the Pond distributed file system showed that computation of a threshold RSA signature consumes roughly 86% of the time required to service writes to small files [12]. We apply the “hash-sign-switch” paradigm of Shamir and Tauman [16] and the distributed key generation protocol of Gennaro et al. [7] to convert any existing secure threshold digital signature scheme into a threshold on-line/off-line signature scheme. We show that the straightforward attempt at proving security of the resulting construction runs into a subtlety that does not arise for Shamir and Tauman's construction. We resolve the subtlety and prove our signature scheme secure against a static adversary in the partially synchronous communication model under the one-more-discrete-logarithm assumption [2]. The on-line phase of our scheme is efficient: computing a signature takes one round of communication and a few modular multiplications in the common case.