@misc{cryptoeprint:1998:024,
author = {John Pliam},
title = {The Disparity between Work and Entropy in Cryptology},
howpublished = {Cryptology ePrint Archive, Report 1998/024},
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.