@misc{cryptoeprint:2007:036,
author = {Eike Kiltz},
title = {Chosen-Ciphertext Secure Key-Encapsulation Based on Gap Hashed Diffie-Hellman},
howpublished = {Cryptology ePrint Archive, Report 2007/036},
year = {2007},
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.