Capability Based Security

Capability-based security is a concept in the design of secure computing systems. A capability (known in some systems as a key) is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights. A user program on a capability-based operating system must use a capability to access an object. Capability-based Security refers to the principle of designing user programs such that they directly share capabilities with each other according to the principle of least privilege, and to the operating system infrastructure necessary to make such transactions efficient and secure. http://en.wikipedia.org/wiki/Capability-based_security

Mar'2009: Guido Van Rossum on thinking about it for Python.