Core Secret – Secret sharing between Bluetooth LE peers on iOS

What is this idea good for?

Who would use it?

Why is it needed?

Some actual uses cases are needed.

Allow me to start you off:

(1) Suppose your office has a safe. Your on-staff accountant has the combination and he supervises all access to the safe. But imagine the difficulties if the accountant fell seriously ill, or if access to the safe was needed on a holiday or weekend when the accountant couldn't be reached. Instead of giving the combination to several people as a backup--and thereby losing accountability--you can divide the combination between 4 people in which any 2 can reconstruct the key.

(2) You and your two fellow executives are flying into country X for important business meetings. The border control at country X is known to sometimes snoop on visitors laptops and smartphones, and even copying data. You and the two other travelers can split up your confidential documents such that all 3 of you must be present at the meeting to extract the confidential information. If one of you is searched at the border crossing, you can truthfully say that you don't know any password or passphrase to documents in your possession; only the assembly of 3 people can bring out the originals.

(3) Your company's long-term computer backups--made on network attached storage or to the cloud--are automatically encrypted. The decryption key can be shared between the system administrators and executives such that any 2 sysadmins or any 3 executives can recover the decryption key.