Cryptology ePrint Archive: BibTeX Citation of Report 2001/049

@misc{cryptoeprint:2001:049,
    author = {Marina Pudovkina},
    title = {A known plaintext attack on the ISAAC keystream generator},
    howpublished = {Cryptology ePrint Archive, Report 2001/049},
    year = {2001},
    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.