@misc{cryptoeprint:2005:405,
author = {Tor E. Bj{\o}rstad and Alexander W. Dent},
title = {Building Better Signcryption Schemes with Tag-KEMs},
howpublished = {Cryptology ePrint Archive, Report 2005/405},
year = {2005},
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.