ZumoDrive made this post: http://blog.zumodrive.com/sometimes-you-have-to-roll-a-hard-six
Colin Percival, maker of Tarsnap, made this reply: http://www.daemonology.net/blog/2010-03-11-zumodrive-rolls-a-hard-six.html
The Hacker News discussion: http://news.ycombinator.com/item?id=1183308