Open design would seem to favor the attacker, because it certainly opens the implementation and perhaps also the design for the attacker to study. Justify that open design overrides this seeming advantage and actually leads to solid security.

Open design allows for much closer inspection of the security system-more awareness of the security practices in place is more likely to reveal vulnerabilities to enable resolving those vulnerabilities rather than their exploitation. Obscurity is an insufficient security mechanism, open design allows a more thorough inspection, and knowing that a design will be open should make designers more careful