Cryptology ePrint Archive: BibTeX Citation of Report 2007/409

@misc{cryptoeprint:2007:409,
    author = {Thomas Shrimpton and Martijn Stam},
    title = {Building a Collision-Resistant Compression Function from Non-Compressing Primitives},
    howpublished = {Cryptology ePrint Archive, Report 2007/409},
    year = {2007},
    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.