Capability-based protection with CHERI

Technical note. CHERI is one research foundation for preventive enforcement in the wider AGIACC vision.

Authority carried by a pointer

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A CHERI capability represents an address together with bounds, permissions, and protected metadata. Hardware constrains the creation and use of capabilities; software establishes the policy. This supports memory protection and can underpin compartment boundaries. See Cambridge’s architecture FAQ.

The runtime completes the design

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Bounds checks do not alone provide a complete lifetime policy, application authorization, or fault recovery. Temporal safety requires an appropriate allocation and revocation design. Compartment isolation depends on the runtime, shared objects, interfaces, and authority granted to each component. CHERIoT’s guide describes one concrete hardware/software design; its properties should not be generalized to every CHERI platform.

For a reference platform, the useful experiment is a named component boundary: what memory and services are shared, what an invalid access triggers, and what the application can safely do afterward. Compatibility and overhead must be measured on that implementation.

Next: Memory safety in AI systems.