Compile time encryption for strings using user-defined literals

I am aware that the new C++ standard allows for user-defined literals and that their generation can be done in compile time.

However, I am quite new to the whole template metaprogramming universe and I'm trying to get some examples going, but still without success, since it's the first time I have contact with this particular feature.

So let's say I have a string:

std::string tmp = "This is a test message";

And I would like to encrypt it at compile time using:

std::string tmp = "This is a test message"_encrypt;

Is it even possible what I'm trying to attempt?

I am currently using VS2015 so any help or feedback is appreciated.