Cryptology ePrint Archive: BibTeX Citation of Report 2003/223

@misc{cryptoeprint:2003:223,
    author = {Simon R. Blackburn, Carlos Cid and Steven D. Galbraith},
    title = {Cryptanalysis of a Cryptosystem based on Drinfeld modules},
    howpublished = {Cryptology ePrint Archive, Report 2003/223},
    year = {2003},
    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.