capabilityboth

Capabilityboth is a concept in capability-based security and access control that describes a mechanism requiring two separate capabilities or proofs to grant access to a resource. It is designed to enforce a conjunctive condition where possessing a single capability is insufficient, thereby supporting dual-control or separation-of-duties requirements.

Mechanism and implementation often involve encoding a conjunction of tokens, certificates, or cryptographic proofs into a single access decision. Access can be enforced at the object-capability boundary, within a policy engine, or by a microkernel. Implementations may use multi-token handshakes, cryptographic signatures, or programmable policy logic to ensure that both capabilities are present and valid before authorization is granted. Capabilityboth is thus compatible with existing capability-based models and can be combined with time-bound, context-aware, or cross-domain policies.

Common use cases include high-assurance environments where dual authorization is essential, such as critical infrastructure, financial systems, and sensitive data handling. It also supports organizational requirements for two-person approval, emergency access procedures, and cross-team collaboration where no single actor should unilaterally control a resource.

Advantages of capabilityboth include stronger access restrictions, clearer separation of duties, and the ability to revoke or rotate one capability without invalidating the other. Challenges involve increased complexity in token management, potential performance overhead, and the need for robust revocation and delegation strategies to prevent token leakage or misuse.

See also: capability-based security, dual control, threshold access, token-based access control.