Reliance on Security Through Obscurity

Always consider whether knowledge of your code or design is sufficient to break it. Reverse engineering is a highly successful discipline, and financially feasible for motivated adversaries. Black-box techniques are established for binary analysis of executables that use obfuscation, runtime analysis of proprietary protocols, inferring file formats, and others.

When available, use publicly-vetted algorithms and procedures, as these are more likely to undergo more extensive security analysis and testing. This is especially the case with encryption and authentication.