Cryptology ePrint Archive: BibTeX Citation of Report 2006/141

@misc{cryptoeprint:2006:141,
    author = {Shahram Khazaei and Mahdi M. Hasanzadeh and Mohammad S. Kiaei},
    title = {Linear Sequential Circuit Approximation of Grain and Trivium Stream Ciphers},
    howpublished = {Cryptology ePrint Archive, Report 2006/141},
    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.