Cryptology ePrint Archive: BibTeX Citation of Report 2011/668

@misc{cryptoeprint:2011:668,
    author = {Piotr K. Tysowski and M. Anwarul Hasan},
    title = {Re-Encryption-Based Key Management Towards Secure and Scalable Mobile Applications in Clouds},
    howpublished = {Cryptology ePrint Archive, Report 2011/668},
    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.