If we want to allow D to fit into various niche markets overlooked by C++, for added security, encryption could be added, where the person compiling encrypted .di files would have to supply a key. That would work only for certain situations, not for mass distribution, but it may be useful to enough people.
I can't imagine a situation where encrypting .di files would make any sense. Such files would be completely useless without the key, so you would have to either distribute the key along with the files or the compiler would need to contain the key. The former obviously makes encryption pointless and you could only make the latter work by attempting to hide the key inside the compiler. The fact that the compiler is open source would make that harder and someone would eventually manage to extract the key in any case. This whole DRM business would also prevent D from ever being added to GCC.
