Quantum Cryptography, or Unforgeable Subway Tokens
The use of quantum mechanical systems, such as polarized photons, to record information gives rise to novel cryptographic phenomena, not achievable with classical recording media: 1) A Verify Only Memory (VOM) that, with high probability, cannot be read or copied by someone ignorant of its contents; 2) the multiplexing of two messages in such a way that, with high probability, either message may be recovered at the cost of irreversibly destroying the other.
Quantum multiplexing can be combined with public-key cryptography to produce unforgeable subway tokens that resist counterfeiting even by an opponent with a supply of good tokens and complete knowledge of the turnstiles that test them.
KeywordsShift Register Quantum Cryptography Quantum Memory Transmitted Photon Jacobi Symbol
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