@misc{cryptoeprint:2010:577,
author = {Neal Koblitz and Alfred Menezes and Igor Shparlinski},
title = {Discrete Logarithms, Diffie-Hellman, and Reductions},
howpublished = {Cryptology ePrint Archive, Report 2010/577},
year = {2010},
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.