Why I Switched to Opaquer for My WPF Project (And Never Looked Back)

For years, the author has been developing .NET WPF applications but faced challenges with protecting their intellectual property while preserving the user interface. After working on a major WPF project targeting .NET 10, they decided to share their experience with Opaquer, a tool that solved their obfuscation problems.

Obfuscating a WPF app with traditional obfuscators often results in UI issues, such as blank windows, failing bindings, and crashes. This is due to the BAML (Binary Application Markup Language) format, which compiles XAML into a binary format embedded in the assembly. When a classical obfuscator renames names in the IL, it must also find and rewrite every reference to those names inside the BAML, making the process difficult and prone to errors.

Opaquer takes a different approach by encrypting the entire BAML resource instead of renaming symbols. The encryption workflow includes obfuscating the IL normally, encrypting the BAML section, and decrypting the BAML in memory at runtime. This ensures that bindings, converters, and events remain functional, and decompilers like ILSpy cannot access the encrypted BAML.

The author reports minimal performance impact from using Opaquer, as the runtime overhead of decrypting BAML is only noticeable once per XAML view. They have been using the free Basic Edition, which includes all major obfuscation algorithms and digital watermarking, without needing the Pro version's command-line interface. With Opaquer, the author has successfully protected their app, maintained a functional UI, and gained peace of mind knowing their XAML structure, bindings, and event handlers are secure.