@misc{cryptoeprint:1999:011,
author = {Victor Shoup},
title = {Practical Threshold Signatures },
howpublished = {Cryptology ePrint Archive, Report 1999/011},
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.