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
timestampingundeniabilityforgery evidenceSchnorr signature
Contact author(s)
przemyslaw kubiak @ pwr wroc pl
History
2013-11-13: received
Short URL
https://ia.cr/2013/730
License
Creative Commons Attribution
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},
      note = {\url{https://eprint.iacr.org/2013/730}},
      url = {https://eprint.iacr.org/2013/730}
}
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