Rama
incipiente de la criptografía que estudia la aplicación de la mecánica cuántica
a la misma. Según el principio de indeterminación de Heisenberg toda medida en
un canal por ejemplo, una interceptación- por el que circulan fotones provoca
perturbaciones que delatan dicha medida. De esta manera, se pueden intercambiar
claves secretas, para ser usadas en criptosistemas simétricos, mediante fotones
portadores de bits, siendo su interceptación percibida por los interlocutores, quienes
así podrán iniciar un nuevo intercambio. [Ribagorda:1997]
Quantum
cryptography, or quantum key distribution (QKD), uses quantum mechanics to
guarantee secure communication. It enables two parties to produce a shared
random bit string known only to them, which can be used as a key to encrypt and
decrypt messages.
An important and
unique property of quantum cryptography is the ability of the two communicating
users to detect the presence of any third party trying to gain knowledge of the
key. This results from a fundamental part of quantum mechanics: the process of
measuring a quantum system in general disturbs the system. A third party trying
to eavesdrop on the key must in some way measure it, thus introducing
detectable anomalies. By using quantum superpositions or quantum entanglement
and transmitting information in quantum states, a communication system can be
implemented which detects eavesdropping. If the level of eavesdropping is below
a certain threshold a key can be produced which is guaranteed as secure (i.e.
the eavesdropper has no information about), otherwise no secure key is possible
and communication is aborted.
The security of
quantum cryptography relies on the foundations of quantum mechanics, in
contrast to traditional public key cryptography which relies on the
computational difficulty of certain mathematical functions, and cannot provide
any indication of eavesdropping or guarantee of key security.
Quantum
cryptography is only used to produce and distribute a key, not to transmit any
message data. This key can then be used with any chosen encryption algorithm to
encrypt (and decrypt) a message, which can then be transmitted over a standard
communication channel. The algorithm most commonly associated with QKD is the
one-time pad, as it is provably unbreakable when used with a secret, random
key.
http://en.wikipedia.org/wiki/Quantum_cryptography
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