leap of faith

Operating a system as though it began operation in a secure state, even though it cannot be proven that such a state was established (i.e., even though a security compromise might have occurred at or before the time when operation began).

The initial part, i.e., the first communication step, or steps, of a protocol that is vulnerable to attack (especially a man-in-the-middle attack) during that part but, if that part is completed without being attacked, is subsequently not vulnerable in later steps (i.e., results in a secure communication association for which no man-in-the-middle attack is possible).

Usage: This term is listed in English dictionaries, but their definitions are broad and can be interpreted in many ways in Internet contexts. Similarly, the definition stated here can be interpreted in several ways. Therefore, IDOCs that use this term (especially IDOCs that are protocol specifications) SHOULD state a more specific definition for it.

Tutorial: In a protocol, a leap of faith typically consists of accepting a claim of peer identity, data origin, or data integrity without authenticating that claim. When a protocol includes such a step, the protocol might also be designed so that if a man-in- the-middle attack succeeds during the vulnerable first part, then the attacker must remain in the middle for all subsequent

exchanges or else one of the legitimate parties will be able to detect the attack.