Roll a dice via e-mail

Question

I have been asked this question, but failed to find an article that describe a good method. Instead I came out with my own method (see my answer below). However it is also possible that I merely came up with a method I am not smart enough to break. So I pass this question on to you:

Alice and Bob wish to play a board game over e-mail. They need to find a way to roll the dice in a way that will not let them cheat.

What is a good algorithm to do so.