James Goodfellow patented the PIN-and-card cash machine so only genuine customers get cash

BBC News reported in 2017 on James Goodfellow, a Kelvin Hughes development engineer in Glasgow who first patented a cash machine using personal identification numbers, in May 1966, more than a year before Barclays unveiled John Shepherd-Barron's machine in 1967. The problem driving the work was Saturday closing: unions were pressing banks to move to a five-day week, so banks wanted a way for working customers to reach their money when branches were closed.

Goodfellow says the challenge was 'how would a genuine customer, and only a genuine customer, get money out of it?' Biometrics such as fingerprints, voice prints or retinal scans were impossible with 1960s technology, so he looked for an 'exotic token'. His 'eureka moment' was the PIN: a number known to the customer and the bank, related to the card but unreadable by anyone else.

His card was a quarter of a Hollerith punch-card, the size of today's credit card, holding 30 bytes. Banks demanded a lot: one million customers and 2,000 machines, any customer able to use any machine, with no IT network in those days. The team submitted around 1,000 cards to a consultant who tried to decipher the code.

Biometrics were not feasible in the 1960s.

A secret number plus a physical card gives two independent checks.

A short code related to the card can be verified without storing readable secrets on it.

Banks needed any-customer, any-machine access, which a standard card and PIN could provide.

When the ideal security technology does not exist yet, combine a possession and a secret using what you can build now.

Goodfellow's patent was licensed by all the manufacturers, though as a technician he did not own the rights and says he got a dollar for each of 15 countries' patents. Shepherd-Barron's machine used carbon-14 cheques and beat Goodfellow's Westminster Bank machines by about a month, but Goodfellow's card-and-PIN became the forerunner of today's system. He received an OBE in 2006 as the patentor of the PIN.