CH1: What is Security Engineering?

from "Security Engineering" by Ross Anderson

To build a dependable system you need

Policy: know what you're supposed to achieve
Mechanism: access controls, hardware tamper resistance, other machinery you use to implement the policy
Assurance: amount of reliance you can place on each particular mechanism, and how well they work together
Incentive: the motive that the people defending your system have to do their job properly, and the motive attackers have to defeat your policy

Example: 9/11 terrorist attacks

This was a failure of policy
Knives up to 3 inches long were permitted!
Screeners were effective at keeping out guns and explosives. So mechanism was ok

Definitions

Subject = a physical person
Principal = an entity that participates in a security system