Apple co-founder Steve Wozniak says the NSW government would face an "almost impossible" task in securing financial data if a plan to allow people to use debit and credit cards on public transport goes ahead.
Transport Minister Andrew Constance on Monday committed to the trial of using financial cards to tap on and off the transport system next year.
Mr Wozniak says financial security breaches are a "horrible problem" worldwide.
"It's almost impossible to guarantee a system is perfectly secure in any sense," he said at a joint press conference with Mr Constance at the Future Transport Summit in Sydney.
"There's flaws in it (every system) because it's software written by humans and the software is so huge and levelled."
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The government's payment plan also raises questions about how data would be used.
Mr Wozniak says the government probably has similar data already and that people had begun to accept privacy trade-offs in their daily lives.
He says groups that gather data should give privacy guarantees but doubted that would happen.
"I don't think you're going to have big statements, 'your data is totally protected' (on public transport)," he said.
Mr Constance said Opal card data had helped plan the integration of the South West Rail Link into the broader network and would play an important role in future projects.
He said the government would work on safety with financial institutions before rolling out its bank card trial.
"We have across the retail sector now, the ability to swipe your credit card at the counter," he said.
"What we're about is making sure that in dealing with the financial institutions we ensure those safeguards are in place."
Mr Constance says he expects the plan to become a reality following the trial, with a similar system already in place in London.
