Two-faced processes and random number generators

We describe random processes (with binary alphabet) whose entropy is less than 1 (per letter), but they mimic true random process, i.e., by definition, generated sequence can be interpreted as the result of the flips of a fair coin with sides that are labeled 0 and 1. It gives a possibility to construct Random Number Generators which possess theoretical guarantees. This, in turn, is important for applications such as those in cryptography.