Randomness and Pseudorandomness

For all of you podcast listeners, Melvin Bragg and his guests recently discussed ideas of randomness and pseudorandomness on the BBC program In Our Time. It was an interesting piece, especially given the fact that the sections of the CATALST course at the University of Minnesota start tomorrow with the iPod Shuffle MEA.

Randomness is the mathematics of the unpredictable. Dice and roulette wheels produce random numbers: those which are unpredictable and display no pattern. But mathematicians also talk of 'pseudorandom' numbers - those which appear to be random but are not.

In the last century random numbers have become enormously useful to statisticians, computer scientists and cryptographers. But true randomness is difficult to find, and mathematicians have devised many ingenious solutions to harness or simulate it. These range from the Premium Bonds computer ERNIE (whose name stands for Electronic Random Number Indicator Equipment) to new methods involving quantum physics.

Digital computers are incapable of behaving in a truly random fashion - so instead mathematicians have taught them how to harness pseudorandomness. This technique is used daily by weather forecasters, statisticians, and computer chip designers - and it's thanks to pseudorandomness that secure credit card transactions are possible.