[sgk284]

We already have functioning quantum cryptography. In theory it should be unbreakable, but there are practical problems with it (distance... it doesn't work around the world) and still relies on humans to implement the systems.

Current quantum cryptography systems have already been cracked to some extent: http://spectrum.ieee.org/computing/it/quantum-cryptography-c...

[Panoramix]

Actually, there are a number of possible attacks against a quantum cryptosystem; e.g. http://en.wikipedia.org/wiki/Quantum_cryptography#Attacks