Cryptology ePrint Archive: BibTeX Citation of Report 2006/104

@misc{cryptoeprint:2006:104,
    author = {Marc Stevens},
    title = {Fast Collision Attack on MD5},
    howpublished = {Cryptology ePrint Archive, Report 2006/104},
    year = {2006},
    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.