Premium Bond - ERNIE

ERNIE

ERNIE (which stands for Electronic Random Number Indicating Equipment) is a hardware random number generator. The first ERNIE was built at the Post Office Research Station by a team led by Sidney Broadhurst. The designers were Tommy Flowers and Harry Fensom. It was unveiled in 1957, and generated its bond numbers based on the signal noise created by a bank of neon tubes. ERNIE 1 is currently on display at the Science Museum in London.

ERNIE 2 replaced the first ERNIE in 1972.

ERNIE 3 was introduced in 1988 and was the size of a personal computer; at the end of its life it took five and a half hours to complete its monthly draw.

In August 2004 ERNIE 4 was brought into service in anticipation of an increase in the number of prizes to be allocated each month from September 2004. ERNIE 4 was developed by LogicaCMG, is 500 times as fast as the original ERNIE and generates a million premium bond numbers an hour; these are then checked against a list of valid bonds to determine the winning bonds before any prizes are awarded. By comparison, the original ERNIE generated 2000 numbers an hour and was the size of a van.

ERNIE 4 uses thermal noise in transistors as its source of entropy for generating true random numbers; the original ERNIE used a gas neon diode. Pseudorandom numbers, often called simply random, can be recreated by anybody who knows the algorithm used to generate them as they are produced in a deterministic way; true random numbers cannot. The randomness of ERNIE's numbers derives from the inherent and unavoidable random statistical fluctuations in the physical processes involved. ERNIE's output is independently tested each month by an independent actuary appointed by the government, and the draw is only valid if the output passes tests that indicate it is statistically random.

ERNIE, anthropomorphised in early advertising, regularly receives cards and letters from the general public.