@misc{cryptoeprint:2008:514,
author = {Tapan Rai and Stanislav Bulygin},
title = {Noncommutative Polly Cracker-type cryptosystems and chosen-ciphertext security},
howpublished = {Cryptology ePrint Archive, Report 2008/514},
year = {2008},
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.