Definition
Capability
A capability is an unforgeable ticket (token) that defines the privileges of its holder.
Subject-Centred
Each capability is associated with a subject. Capabilities are usually implemented via random strings (cryptographically protected, e.g. via HMAC) or controlled by the operating system. They can be passed from one subject to another.
Token Validity
The reference monitor checks only the validity of the token. There is no need to identify the subject.