The final dependency that must be satisfied in order to create an evolution engine is the random number generator (RNG). An evolution engine has a single RNG that it passes to its candidate factory, evolutionary operator and selection strategy. An ideal RNG is both fast and statistically random. We could use the standard Java RNG, java.util.Random, but its output is not as random as it should be. The other RNG in the standard library, java.security.SecureRandom is much better in this respect but can be slow.