Cryptology ePrint Archive: BibTeX Citation of Report 2009/253

@misc{cryptoeprint:2009:253,
    author = {Cas J.F. Cremers},
    title = {Formally and Practically Relating the CK, CK-HMQV, and eCK Security Models for Authenticated Key Exchange},
    howpublished = {Cryptology ePrint Archive, Report 2009/253},
    year = {2009},
    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.