@misc{cryptoeprint:2006:278,
author = {Alexander W. Dent},
title = {Fundamental problems in provable security and cryptography},
howpublished = {Cryptology ePrint Archive, Report 2006/278},
year = {2006},
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.