Quantum cryptography, a new technology until now considered 100 percent secure against attacks on sensitive data traffic, has a flaw after all, Swedish researchers said on Friday.

“In computer terms, we've found a bug,” said Jan-Aake Larsson, an associate professor of applied mathematics at the Linkoeping University in southern Sweden.

“It was surprising,” he told AFP.

“We didn't expect to find a flaw,” he said, adding that he and another researcher at the university had also discovered a way to fix the problem.

Many experts hope quantum cryptography will be the answer to growing fears about data security on the Internet, providing a one-off code that would be unbreakable for hackers.