Quackers: Quantum cryptography not what it's cracked up to be

Joining the long list of technological promises that don't quite make the grade such as "Nuclear: too cheap to meter" and the oxymoron "3G Broadband" is quantum cryptography. Quantum hackers known as 'quackers' have a few ways in to breach quantum cryptography already, and this trend will continue.

Quantum cryptograpy is meant to be a system that can detect interception of the photons comprising a communication by a hacker flawlessly. It is meant to be perfect, and not just a step foward. It is already crackable, though, albeit through high faluted means.

In quantum messages, the message is sent through traditional means, but the encryption key (called a 'one time pad' or OTP) is transmitted using the quantum states of individual photons. The theory is that you cannot read a bit of the OTP without changing its quantum state, so therefore any hack attack will be noticed, and a new key can be created to replace the compromised key. Quantum crypotgraphers encode keys rather than the message because transmission rates are low (currently a few kbps over 20km), though this will improve with faster detectors.

Quackers exploit several weaknesses here, mainly focused on the quantum/silicon interface.

Problem: practically producing single photons is challenging. If there's more then one photon encoding a bit, then the quacker can read one, and the receiver reads another that has not been disturbed. Therefore the receiver will not detect the intrusion.
Solution: better lasers that can accurately issue single photons. Needs time to make this happen.

Problem: saturating the detector with strong light allows control without detection of the signals
Solution: requires physical access to detector, and more advanced detectors could be make without this flaw

Problem: any connection to a public network allows traditional hacking
Solution: restrict quantum crptography to closed networks, but this limits its usability for the general world

Problem: quantum bits get interpreted into electrons so they can be used. This happens sometime before the user's computer/server, so is necessarily hackable by traditional means.

The point here is not that quantum cryptography isn't very secure, because it's by far the best there is. My point is that it is not flawless. Quantum cryptography is an additional line of defence, but sadly not flawless. It's not a 'quantum leap' in security (to use a pun), just a (very good) forward step in the cat-and-mouse game between networks and hackers.