Cryptology ePrint Archive: BibTeX Citation of Report 2008/464

@misc{cryptoeprint:2008:464,
    author = {Michael Kounavis and Shay Gueron},
    title = {Vortex: A New Family of One Way Hash Functions based on Rijndael Rounds and Carry-less Multiplication},
    howpublished = {Cryptology ePrint Archive, Report 2008/464},
    year = {2008},
    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.