For those who don't understand cryptographic one-way hashes, they cannot be reversed to produce the original data without a dictionary attack. A dictionary attack in this case would require a collection of actual human fingers or replicas of them to run through Apple's Touch ID to see which cryptographic hashes match the one stored on the device.
Also note, that their is a really really really small chance that two fingerprints will generate the same cryptographic hash. Cryptographic hashes by their very nature have LESS data than the source data for which they are hash. This means that the if the source data has potentially quadrillions of combinations that there may be only billions of values that they hash to (a one to many mapping of hashes to source data). More likely scenario is that your fingerprint hashes to the same value as a fingerprint that does not currently exist on the planet today and may never exist.
Think of a large 500-page book as a just a collection of letters, numbers, spaces, and punctation. You could pound on the keyboard and produce a book of random text or you could carefully craft an actual readable book. The hash reduces the book to a hash of say 500 characters which is generated in such a way that even changing a single letter in the book or the capitalization of a single letter produces an entirely different hash (cryptographic hash algorithms magnify any change to cyclically change other parts). Obviously, there is no way you could take 500 characters of data and regenerate the 500-page book (that would be the most amazing lossless-compression algorithm in the world, but also mathematically impossible). Because of this you cannot reverse it. You could however, run a hash on all books known to man to find the one that matches the same value (a dictionary attack). Finally, there is a possibility that two carefully crafted books hash to the same value, but it is far more likely that a book's hash would match some of the billions of permutations of random letters , numbers, spaces, and symbols that have never been bound into a book.
It is the same for fingerprint data. Your actual fingerprint could only be determined if somebody already had a replica of your finger in a database and could make Apple's Touch ID sensor generate the same hash from it. The worst somebody could do is break into your phone or prove that a phone did indeed belong to you. What's more, the odds of somebody else's fingerprint matching yours is like two monkeys pounding out the exact same content on a keyboard after an hour of bashing away at it. Either way, there is no chance of your fingerprint being cloned and used in other places to impersonate your presence.
