Abstract: A capability based computer system includes means, called a factory, for allowing two domains to share resources in a secure manner. Factories are special domains which, in combination with corresponding kernel functions, allow a first domain (called a builder domain) to install a program and other components in a factory for use by other domains, and then to seal the factory, thereby leaving the builder domain with no keys to the factory except a special type of entry key called a requestor key.The holders of requestor keys can use the program in the factory by invoking the requestor key. This causes the factory to set up a new special domain for the requestor which allows the requestor to use the program in the factory to process data without being able to inspect the program. Further, the factory mechanism includes means for the requestor to confirm that the factory includes no keys which could compromise the confidentiality of the requestor's data.