Cryptology ePrint Archive: BibTeX Citation of Report 2011/586

@misc{cryptoeprint:2011:586,
    author = {Mainack Mondal and  Avik Chakraborti and Nilanjan Datta and Debdeep Mukhopadhyay },
    title = {TweLEX: A Tweaked Version of the LEX Stream Cipher},
    howpublished = {Cryptology ePrint Archive, Report 2011/586},
    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.