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