The Bank for International Settlements (BIS) published in
August, 1996, "Security of Electronic Money," a long,
detailed study. Compare this architecture to Anderson/Kuhn's
and Biham/Shamir's recent demolition.
The orginal is available at:
http://www.bis.org/publ/cpss18.pdf
Better, Ian Grigg has HTML-ed it at:
http://www.systemics.com/docs/papers/BIS_smart_security.html