Cryptology ePrint Archive: BibTeX Citation of Report 2013/730

@misc{cryptoeprint:2013:730,
    author = {{\L}ukasz 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, Report 2013/730},
    year = {2013},
    note = {\url{http://eprint.iacr.org/}},
}

You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.