Cryptology ePrint Archive: BibTeX Citation of Report 2004/134

@misc{cryptoeprint:2004:134,
    author = {Elisabeth Oswald and Stefan Mangard and Norbert Pramstaller},
    title = {Secure and Efficient Masking of AES - A Mission Impossible?},
    howpublished = {Cryptology ePrint Archive, Report 2004/134},
    year = {2004},
    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.