Introduction

Commercial security is a matter of solving the practical problems of business relationships such as privacy, integrity, protecting property, or detecting breach of contract. A security hole is any weakness that increases the risk of violating these goals. In this real world view of security, a problem does not dissapear because a designer assumes it away. The invocation or assumption in a security protocol design of a "trusted third party" (TTP) or a "trusted computing base" (TCB) controlled by a third party constitutes the introduction of a security hole into that design. The security hole will then need to be plugged by other means.

If the risks and costs of TTP institutional alternatives were not accounted for in the protocol design, the resulting protocol will in most cases be too costly or risky to be practical. If the protocol beats these odds and proves practical, it will only succeed after extensive effort has gone into plugging the TTP security hole(s). TTP assumptions cause most of the costs and risks in a security protocol, and plugging TTP security holes produces the most benefit and profit.

As a result, we propose a security protocol design methodology whereby the most risky and expensive part(s) of a security protocol, the trusted third partie(s), are designed in parallel with security protocol(s) using those parties. The objectives of cost and risk minimization are focused on the TTPs rather than the security protocols themselves, which should be designed to suit the cost and risk minimized TTPs.

We also briefly discuss and reference research and implementation in security mechanisms that radically reduce trusted third party costs and risks by distributing automated TTPs across several parties, only a portion of which need to act in a reliable or trustworthy matter for the protocol to be reliable or trustworthy.