Cambridge CAP computer

The Cambridge CAP computer was an experimental research machine built at the University of Cambridge Computer Laboratory between 1970 and 1977 under the direction of Maurice Wilkes and Roger Needham, with David Wheeler overseeing its implementation, and it became fully operational in 1976. It is described as the first successful experimental computer to demonstrate capability based security in both hardware and software, a protection scheme in which any process wanting to access a memory segment or piece of hardware had to hold an explicit capability granting that access. Beyond its research role the CAP also ran as a working service computer at Cambridge, making it a rare case of a security research platform that was also used for everyday computing.