When Michael Turner started at the BNZ in his mid-20s, he was stuffing credit cards into envelopes in the mailroom.
Now, aged 46, he has invented a system to prevent one the most common causes of credit card fraud.
Mr Turner's system is known as "liquid encryption number" which the
bank revealed yesterday it has patented and hopes to sell internationally.
It prevents skimming, which involves criminals recording customers' credit card details to use later.
The system keeps changing the card details so when criminals go to use the stolen information, it is old and does not work.
Mr Turner said yesterday that he did not have a technical background but came up with the idea after many years of thought and research.
"It just married together and then suddenly all these little lights started going off," he said.
"I needed a lot of people to help and there's a lot of specialist people involved in different parts of itthat all had to work together."
The invention's name has a dual meaning. It is termed "liquid" because it changes constantly, but is also named after another BNZ employee, Len Lynskey, who was one of the lead developers of the system.
"I was the one that came up with the idea but there were several problems to solve along the way that he was instrumental with to make it work technically."
Mr Turner, who was born in Christchurch but lives in Wellington, said he was rapt to have created something that prevented fraud.
"One of the most amazing things is you wake up on a Sunday morning with an idea, then you write it down, and next thing you see it's working around the whole world. That's pretty bizarre, but fantastic."
The BNZ says that since the system was introduced, skimming has halved.
HOW IT WORKS
* Liquid encryption number technology means that the data - a series of numbers - stored on a card keeps changing.
* The data on a card's strip is rewritten each time the card is placed in an ATM.
* By the time criminals try to use the card, its data will have changed so it cannot be used in fraudulent transactions.
