Cryptology ePrint Archive: BibTeX Citation of Report 2015/528

@misc{cryptoeprint:2015:528,
    author = {Sunoo Park and Krzysztof Pietrzak and Jo\"el Alwen and Georg Fuchsbauer and Peter Gazi},
    title = {Spacecoin: A Cryptocurrency Based on Proofs of Space},
    howpublished = {Cryptology ePrint Archive, Report 2015/528},
    year = {2015},
    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.