Cryptology ePrint Archive: BibTeX Citation of Report 2012/623

@misc{cryptoeprint:2012:623,
    author = {David McGrew},
    title = {Impossible plaintext cryptanalysis and probable-plaintext collision attacks of 64-bit block cipher modes},
    howpublished = {Cryptology ePrint Archive, Report 2012/623},
    year = {2012},
    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.