American researchers have developed artificial fingerprints, claiming they could hack into a third of smartphones.
Scientists from New York University and Michigan State University told CNBC that the so-called 'DeepMasterPrints' can mimic more than one in five fingerprints.
Fingerprint systems usually only record part of a print, making it easier to fake than complete prints.
"If you store images for three of your fingers the device may keep around 30 partial fingerprints," the researchers said. "With MasterPrints you just have to create a few - five or 10 and I'm in business."
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They reckon the prints can unlock just under a third of phones, and only every fifth phone they attempt needs to work for the scam to be a success.
They justified their research by saying security researchers need to stay ahead of hackers.
"Research in assessing vulnerabilities in a fingerprint recognition system is a constant arms race between fixing vulnerabilities and discovering new ones," their paper said. "It is important for researchers to probe for new vulnerabilities so that loopholes can be fixed."
The least secure smartphone fingerprint detectors are those on the sides, rather than the front or back - they're more convenient but thinner, requiring less of a fingerprint to unlock.
The paper was presented at a security conference in Los Angeles recently.