Dual control

Dual control requires two or more authorised people to participate at the same time before a single sensitive action can complete. Opening a vault, releasing a high-value payment, or activating a master cryptographic key are the classic cases: the operation is a single event, and one person acting alone, whether by mistake or by intent, is a risk the organisation refuses to carry.

The control is easily confused with separation of duties, which splits a workflow across different people at different stages. The difference is timing. Separation of duties puts people at different points in a process; dual control puts them on the same action at the same moment. In key management, dual control is usually combined with split knowledge, where each custodian holds only part of the key material, and generalised as M-of-N control, where any M of N custodians must take part. Recovering a key held in key escrow normally works the same way.

Dual control removes the single-actor path but not collusion: if the two people coordinate, the control fails by design, which is why it is layered with job rotation, mandatory vacations and independent audit.

Exam relevance: scenarios in this area tend to describe a process and ask which control it shows. Two people acting together on one operation points to dual control; different people at different stages points to separation of duties. A mention of collusion usually signals that a complementary control, not a second person, is the expected answer.