Cryptology ePrint Archive: BibTeX Citation of Report 2013/881

@misc{cryptoeprint:2013:881,
    author = {Yonatan Sompolinsky and Aviv Zohar},
    title = {Accelerating Bitcoin's Transaction Processing. Fast Money Grows on Trees, Not Chains},
    howpublished = {Cryptology ePrint Archive, Report 2013/881},
    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.