Prototype of a Quantum Cryptography System for the End User

It is known that the quantum cryptography protocols are able to detect immediately any attempt to attack the key generation and the exchange process. The well-known BB84 protocol (C. Bennet e G. Brassard 1984) uses the quantum property which states that orthogonally polarized states can be completely discriminated, thus can be used to codify information. The developed system adopts a properly costumized BB84 protocol. The hardware instrumentation includes two fast PCs with acquisition card, a 4-channels transmitter, 4 high-efficiency LED diodes, a receiver with 4 high-sensitivity avalanche photodiodes, and suitable optical devices. Transmitter and receiver have been realized by means of two custom electronic cards, that are driven by two separated PCs with suitable software devoted to the signal generation and decoding procedures. The system is a prototype that can be further improved in order to be used in end user money transactions and to allow each one to afford the quantum cryptography security level. The system can be further downsized to develop quantum cryptography circuits embeddable in mobile devices to ensure the maximum security in money transfer and controlled access.