Patent ID: 7606367
Filing Date: 2009-10-20
Classification: H04L

Abstract:
1. A method for exchanging a secure cryptographic key for a quantum cryptography apparatus employing non-ideal elementary quantum states, wherein the apparatus comprises an emitter and a receiver, being connected by a quantum channel and a conventional communication channel, the emitter choosing a block size N, wherein N>=2, the receiver using the same said block size N, the emitter generating a random bit for each block to define an encoding basis, the receiver generating a random bit for each block to define a measurement basis, the emitter encodes blocks of N bits at random onto a number of non-orthogonal states belonging to at least two suitable sets, where the same encoding basis is used for all N bits within a given block, the receiver randomly chooses the analysis measurement for every block of N bits within said suitable sets, where the same measurement basis is used for all N bits within a given block.