Here is their main intro.
Controversy concerning the quality of anonymity is described here.
Michael Froomkin has written on
legal aspects of digital anonymity.
Here is a protocol that I devised that was inspired by early rumors of the Mondex card.
Stories about a break in to Mondex.
Stuff above was written when Mondex was just a couple of years old.
A search today (Sept 2005) yields these notes.
1997 June Overview;