Ran, present agenda, skip intro and move to presentations. Role policy defines roles and mapping rights roles, and then identifies access control by saying who may assume which roles. Access control policy.
Roles are collection of access rights.
People join and leave over varying amounts of time with a key tree at each point in time. Looks like OFT, but does not need to be hashed, just generated. BHT per ADU key calculation. Basic concept has 2 key servers each with one member with a person at key server 1. HH asserts that there is some interaction between key servers.