KeyKOS

KeyKOS is a capability-based operating system and microkernel project that originated in the 1980s from Key Logic, Inc. It is characterized by its focus on secure, object-oriented computation and a distributed, persistent computing model. In KeyKOS, security and access control are implemented through capabilities—unforgeable references that grant specific rights to objects such as data stores, processes, and services.

The architecture centers on a small kernel that provides essential interprocess communication and protection primitives, while most system services run as user-space servers. Everything in KeyKOS is treated as an object, and access is controlled by capabilities carried by the invoking process. This results in fine-grained, portable security: capabilities can be created, delegated, and restricted to define who may do what with which object. A notable aspect of KeyKOS is object persistence: objects and their state can outlive the processes that manipulate them, enabling durable storage and recovery across reboots.

KeyKOS was designed with distribution in mind, supporting networked use and the sharing of capabilities across machines. Its model promotes secure collaboration by enabling controlled delegation of authority without central authentication checks at every operation. The system inspired a lineage of later capability-based research and development, influencing subsequent projects in the capability-based OS space.

Today KeyKOS is no longer actively developed, but it remains a historically significant example of early capability-based design. It contributed to discussions of persistent object stores, secure delegation, and distributed, object-centric computing, and it informed later research-oriented systems such as EROS and other capability-based operating systems.