US Patent 9184912 Secure quantum authentication system

A method and apparatus for sharing information. First bits are selected from a shared secret key in a first device. The first bits have a selected length. Second bits with the selected length in signals are sent from the first device to a second device. The signals have selected types of properties based on the first bits. The second bits are encoded in states for the selected types of properties. A key is generated in the first device. The key is based on the second bits received at the second device having the selected types of properties identified as matching expected types of properties.