@misc{cryptoeprint:1999:014,
author = {Ivan Damgard },
title = {Concurrent Zero-Knowledge is Easy in Practice },
howpublished = {Cryptology ePrint Archive, Report 1999/014},
year = {1999},
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.