[dfox]

Interesting possibility in white-box model is ability to take something invertible (eg. block cipher) and instantiate it in a way that cannot be inverted. That would allow for building fixed key signature mechanism with essentially arbitrary signature size equal to security level.

Another question is whether usable (ie. reasonable code and data sizes) and secure (with "hard" in the cryptographic sense, not in the sense of non-obvious) white-box cryptography is actually possible.