Random and Pseudorandom

Melvyn Bragg and his guests discuss randomness and pseudorandomness.

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.

With:

Marcus du Sautoy
Professor of Mathematics at the University of Oxford

Colva Roney-Dougal
Senior Lecturer in Pure Mathematics at the University of St Andrews

Timothy Gowers
Royal Society Research Professor in Mathematics at the University of Cambridge

Producer: Thomas Morris.