Stamp \& Extend -- Instant but Undeniable Timestamping based on Lazy Trees

Łukasz Krzywiecki; Przemys{\l}aw Kubiak; Miros{\l}aw Kuty{\l}owski

Paper 2013/730

Stamp \& Extend -- Instant but Undeniable Timestamping based on Lazy Trees

Łukasz Krzywiecki, Przemys{\l}aw Kubiak, and Miros{\l}aw Kuty{\l}owski

Abstract

We present a Stamp\&Extend time-stamping scheme based on linking via modified creation of Schnorr signatures. The scheme is based on lazy construction of a tree of signatures. Stamp\&Extend returns a timestamp immediately after the request, unlike the schemes based on the concept of timestamping rounds. Despite the fact that all timestamps are linearly linked, verification of a timestamp requires a logarithmic number of steps with respect to the chain length. An extra feature of the scheme is that any attempt to forge a timestamp by the Time Stamping Authority (TSA) results in revealing its secret key, providing an undeniable cryptographic evidence of misbehavior of TSA. Breaking Stamp\&Extend requires not only breaking Schnorr signatures, but to some extend also breaking Pedersen commitments.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Published elsewhere. Chris J. Mitchell and Allan Tomlinson, editors, INTRUST, volume 7711 of Lecture Notes in Computer Science, pages 5–24. Springer, 2012.
DOI: 10.1007/978-3-642-35371-0_2
Keywords: timestamping undeniability forgery evidence Schnorr signature
Contact author(s): przemyslaw kubiak @ pwr wroc pl
History: 2013-11-13: received
Short URL: https://ia.cr/2013/730
License: CC BY

BibTeX

@misc{cryptoeprint:2013/730,
      author = {Łukasz Krzywiecki and Przemys{\l}aw Kubiak and Miros{\l}aw Kuty{\l}owski},
      title = {Stamp \& Extend -- Instant but Undeniable Timestamping based on Lazy Trees},
      howpublished = {Cryptology {ePrint} Archive, Paper 2013/730},
      year = {2013},
      doi = {10.1007/978-3-642-35371-0_2},
      url = {https://eprint.iacr.org/2013/730}
}