A senior US senator believes the fingerprint recognition technology featured in Apple's new iPhone 5S raises "substantial privacy questions".
Senator Al Franken, chairman of the influential Senate Judiciary Subcommittee on Privacy, Technology and the Law, has written to Apple boss Tim Cook explaining his security concerns.
After stealing someone's thumbprint, hackers could "impersonate you for the rest of your life," he wrote.
Apple has yet to comment on the letter.
Mr Franken wants answers to a number of questions, such as:
Mr Franken has asked Apple to answers his questions within a month of receiving his letter.
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