Apple has gone out of its way to emphasize the secure, locked down nature of its Touch ID fingerprint scanning system, but Senator Al Franken still believes the technology "raises substantial privacy questions." As a result, he's written a letter to CEO Tim Cook requesting more specifics on Touch ID. Franken seems well versed on the information Apple has released thus far, acknowledging that fingerprint data is stored in a dedicated, secure enclave of the A7 chip. But the Minnesota lawmaker says "important questions remain about how this technology works" and Apple's future plans for Touch ID.

Franken begins by asking whether it's possible to convert fingerprint data into a "digital or visual format" that could potentially be read by third parties. Apple has already answered this definitively on its Touch ID FAQ page: the technology "stores only a mathematical representation" of a user's fingerprint. Franken also requests clarification on whether Touch ID data can be extracted from an iPhone in the first place. (This would be virtually impossible, according to Apple.) He calls out the location tracking controversy Apple faced in 2011, apparently looking to ensure that Touch ID won't go down a similar path.

Franken seeks Apple's assurance that it will never share fingerprint data with governments without due process. He's particularly concerned about snooping and secretive National Security Letters (NSLs), asking Apple to clarify where Touch ID stands as it relates to the FBI and other intelligence agencies. But again, considering that all Touch ID data is stored locally on your device, Apple never sees your fingerprint information. That means the company has nothing to share with authorities. And finally, Franken directly asks Cook whether Apple's users have "any reasonable expectation of privacy" — the same phrase that brought Google a heap of undeserved controversy last month. Franken ends the letter with a request that Apple respond within one month's time.