Cryptology ePrint Archive: BibTeX Citation of Report 2012/158

@misc{cryptoeprint:2012:158,
    author = {Peter Gazi and Stefano Tessaro},
    title = {Efficient and Optimally Secure Key-Length Extension for Block Ciphers via Randomized Cascading},
    howpublished = {Cryptology ePrint Archive, Report 2012/158},
    year = {2012},
    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.