Cryptology ePrint Archive: BibTeX Citation of Report 2011/201

@misc{cryptoeprint:2011:201,
    author = {Lei Wei and Christian Rechberger and Jian Guo and Hongjun Wu and Huaxiong Wang and San Ling},
    title = {Improved Meet-in-the-Middle Cryptanalysis of KTANTAN},
    howpublished = {Cryptology ePrint Archive, Report 2011/201},
    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.