If my post on Voltage Security peaked your interested in IBE (Identity-Based Encryption), check out O'Reilly interview with Terence Spies (cool last name for a security startup VP ;-), VP of Engineering at Voltage Security.  If you are math-enabled or just want to roll your eyeballs, this page is a good starting point.  BTW, some parts of Voltage's IBE technology is patented.  But this shouldn't surprise anyone since VCs are not likely to invest in a patentless security company.