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Quantum Computing Not an Imminent Threat To Public Encryption
Bruce Schneier's latest blog entry points out an interesting analysis of how quantum computing will affect public encryption. The author takes a look at some of the mathematics involved with using a quantum computer to run a factoring algorithm, and makes some reasonable assumptions about the technological constraints faced by the developers of the technology. He concludes that while quantum computing could be a threat to modern encryption, it is not the dire emergency some researchers suggest.
Uff, I meant Applied Cryptography . Practical Cryptography is a bit too basic an overview written with a co-author.
Bruce didn't actually write that article. He only linked to it on his blog, which isn't particularly relevant. And, although Bruce is a brilliant cryptographer, he doesn't know squat about quantum computers, nor does the person that wrote that article. One of the most glaring errors is corrected in comment posted on the article page. Besides that, his argument isn't completely sound. The biggest problem with quantum computers isn't managing to build one with a tons of quantum gates, it's getting the error rate down on the components. If you do that, you ought to be able to build as many gates as you want with enough effort and money. The author's argument seems akin to saying we couldn't possibly build a 100-billion transistor count processor today. We could, its just going to be very expensive and you're not going to mass-produce it.
Right now a lot of people working in the field say quantum computers are about 40 years off. The scary thing though is how its likely to play out. For a few decades quantum computers will likely remain "40 years off" (in the fusion sense), but then someone is going to figure out how to get the error rates below threshold, and then quantum computers will be only 10 years away. That doesn't give us much time to stop using our favorite public key algorithms. That's too bad for nTru; (they have a public key system that is likely resistant to quantum computers), their patents will be long expired.
Your data is both encrypted and unencrypted at the same time, only reverting to one state or the other when you observe it and collapse the waveform. There is also, if I read this correctly, some chance that it will turn into a cat.
Hope that clears it up for you...