One of the first real web pages I put up was a small set of tutorials on how basic crypto algorithms work. This was back in the days (mid 90s) when people actually tended to sit down and roll their own – for fun, for avoiding crypto export regulations (zounds!), and because you couldn’t just fire up python and say “encrypt this, plz”.
For old times’ sake I’ve put them back up as a google site, though I don’t expect to get traffic and emails about them like I used to 
Nevertheless, despite the intro page assertion to the contrary, I’m tempted to add a few new bits. Perhaps a tutorial on differential cryptanalysis, and one on my favorite paper of all time, Claude Shannon’s exposition on information theory and entropy.
