A method for random number generation includes generating random number sequences using a Random Number 5 Generator (RNG) circuit having an externally-modifiable configuration. The RNG circuit generates a first random number sequence having a first measure of randomness, and modifies the configuration of the RNG circuit, causing the RNG circuit to generate a second random number sequence having a second measure of the randomness, indicating a degree of the randomness that is no less than the first measure.