Cryptology ePrint Archive: BibTeX Citation of Report 2006/242

@misc{cryptoeprint:2006:242,
    author = {Haina Zhang , Shaohui Wang, Xiaoyun Wang},
    title = {The Probability Advantages of Two Linear Expressions in Symmetric Ciphers},
    howpublished = {Cryptology ePrint Archive, Report 2006/242},
    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.