Cryptology ePrint Archive: BibTeX Citation of Report 2011/262

@misc{cryptoeprint:2011:262,
    author = {Mohamed Ahmed Abdelraheem and Julia Borghoff and Erik Zenner},
    title = {Cryptanalysis of the Light-Weight Cipher A2U2 - Reduced draft version},
    howpublished = {Cryptology ePrint Archive, Report 2011/262},
    year = {2011},
    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.