Cryptology ePrint Archive: BibTeX Citation of Report 1998/006

@misc{cryptoeprint:1998:006,
    author = {Ronald Cramer and Victor Shoup},
    title = {A Practical Public Key Cryptosystem Provably Secure against Adaptive Chosen Ciphertext Attack},
    howpublished = {Cryptology ePrint Archive, Report 1998/006},
    year = {1998},
    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.