A pattern of interaction undertaken in the expectation of mutual benefit we call a pattern of cooperation . As the Cheyenne Mountain example shows, complete safety is achievable when no cooperation is needed. Similarly, imagine a timesharing system in which all programs execute in system-mode inside one giant address space. All patterns of cooperation possible in computation are clearly possible in this system, but the participants have no safety from each other . Were this timesharing system and its users all in that vault under Cheyenne, they would still be safe from outsiders, but again, this is uninteresting.
Commerce raises many examples of real security issues.
In commerce one often needs to cooperate safely with those one doesn't trust. A shop is willing to be open to outsiders only because its cash register isn't. The shop is neither fully open nor fully closed. In anticipated e lectronic commerce the interactions take place electronically, the agents are running computer programs, and many transactions happen with no human awareness. This environment is sufficiently different that simple analogies are misleading.