This is pretty think, but interesting: http://tf.nist.gov/sim/Papers/Trigo_CPEM_2010.pdf -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk at FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.