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Quantum leaps

It's not Star Trek, but quantum computing looks set to revolutionise the way we do computing.



commentary It's not Star Trek, but quantum computing looks set to revolutionise the way we do computing.

I had relegated anything to do with Quantum Computing to the "I won't hold my breath" category, much like Holographic Mass Storage. The latter I have been waiting for since the 80s -- remember in the '80s this was a truly massive amount of storage. Of course this has not eventuated, I feel partly because those wizards that design hard drives were pulling one engineering innovation after another out of a hat until we we were at the terabyte frontier, and at incredibly low cost per GB. But quantum computing, well at least some forms of it, will be available any day now.

Don't worry, the CIA does not have a quantum supercomputer that I know of that can crack your 256-bit AES in seconds. They do, however, have a supercomputer with plenty of grunt -- though it's not a patch on a hypothetical quantum computer.

What has surfaced is something that probably gives code breakers nightmares and cold sweats at 3am in the morning -- quantum encryption.

Quantum Computing, well at least some forms of it, will be available any day now.
The problem with any traditional form of encryption is that given enough computing power, it can generally be broken by brute force attacks -- admittedly many of the encryption schemes are so computationally intensive as far as brute force decryption is concerned that the oceans would have dried up before the current crop of computers could crack them. But there has always been the spectre of a computer surfacing that is powerful enough, hence the focus on quantum encryption.

Encryption relies on convoluted mathematical algorithms that (hopefully) only have one solution -- the right one. Quantum encryption exploits the laws of physics that include some wonderful and mind-bending quirks of sub-atomic particles to ensure the encryption is more secure.

One of the quirks that Einstein called "spooky action at a distance" is that you can generate two photons that are truly identical twins which are "paired". If you change the state of one of the photons the other will copy that change immediately, even if it is located at the other side of the universe. This weird behaviour, called quantum entanglement, appears to defy some of the traditional laws of physics, and asks how the change can occur immediately and what propagated the message to the other photon to change faster than the speed of light. But this is not our problem. There is another quirk -- when a subatomic particle's state is "read" the state of the particle is altered by the act of reading it.

One third property needs to be added here -- that is the ability to "timestamp" a photon. Each photon will be "expected" at a precise time so you cannot suck the data out of the optic fibre, read it, and then retransmit a regenerated and correct version of the data without upsetting the timing.

Put these three items together and you have a foolproof method of detecting if you have an eavesdropper on your data stream -- both the receiver and the original sender will know if their message data has experienced any tampering.

In the past you couldn't generate enough entangled photons with the required data properties fast enough. The equipment only produces small numbers of photons and tended to overheat and fail. Toshiba has demonstrated a system that has run reliably for four weeks at a stretch and can work over 120km of optic fibre. Its system has another claim to fame, in that it can generate 256-bit encryption keys at a rate of 100-per-second.

This means you could pump your encrypted video through to the receiver along with the quantum keys. If the keys are intercepted you will know about it immediately and if the keys are not intercepted it is going to take a hell of a long time for the bad guys to brute force decrypt every frame of your video stream.

Steven Turvey is Lab Manager of the RMIT IT Test Labs. Send feedback to edit@zdnet.com.au.

This article was first published in Technology & Business magazine.
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