, The Register 2005-04-28
Quantum cryptography - long the stuff of cyberpunk novels and hi-tech spy stories - is leaving the laboratory and making its way into commercial markets. A briefing session at the UK's Department of Trade and Industry on Wednesday featured demonstrations of working quantum key exchange systems by QinetiQ, Toshiba Cambridge and US start-up MagiQ.
Roger
http://en.wikipedia.org/wiki/Quantum_cryptography
Briefly, you are correct; to defeat a MITM attack where the MITM completely replaces one signal with another, an out of band method is used. However the security requirements for the out of band channel are much weaker than us...
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