Cryptology ePrint Archive: BibTeX Citation of Report 2011/664

@misc{cryptoeprint:2011:664,
    author = {S. Sharmila Deva Selvi and S. Sree Vivek and Dhinakaran Vinayagamurthy and C. Pandu Rangan},
    title = {On the Security of ID Based Signcryption Schemes},
    howpublished = {Cryptology ePrint Archive, Report 2011/664},
    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.