@misc{cryptoeprint:2006:053,
author = {J. J. Climent and E. Gorla and J. Rosenthal},
title = {Cryptanalysis of the CFVZ cryptosystem},
howpublished = {Cryptology ePrint Archive, Report 2006/053},
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.