@misc{cryptoeprint:2006:466,
author = {Jason E. Gower},
title = {Prime Order Primitive Subgroups in Torus-Based Cryptography},
howpublished = {Cryptology ePrint Archive, Report 2006/466},
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.