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Quantum computing and cryptography is a whole different ball of wax.

Anyone able to "observe" the passing of the data will, by necessity of Heisenberg's Uncertainty Principle, also alter that data and will cause a communications failure that is easily detected. Therefore only unobserved data is exchanged properly.

Interesting stuff, indeed!

So what happens when our ISPs run a virus scan on our incoming emails or when our own virus scanners check the data...

^The encryption is only on a per-link basis. The points between links such as routers and the servers the ISPs use are fair game.

When you and your ISP both set up a pair of quantum computers.... I doubt you will be running Windows, so no need for virus scans.

http://science.slashdot.org/article.pl?sid=08/06/13/1255208

"Quantum encryption is perfectly secure, in theory. In practice, however, there are loopholes. Now Japanese scientists have designed a quantum eavesdropper that exploits one of these loopholes to listen in to quantum conversations. QC's security arises from the impossibility of making a perfect copy of a quantum object without destroying it — so the sender and receiver can always tell if they've been overheard. But it turns out that an eavesdropper can make imperfect copies and use them to extract information from a quantum message without alerting sender or receiver "

Quantum encryption doesn't rely on complexity as it relies on data integrity. An intercepted key or transmission alters the data. So a third party quantum computer sniffing will change the data.

I think of it this way. Computer A is passing a specific Jenga block stack to Computer B. Any sniffing computer will have to remove blocks to "observe" them. What happens to the tower? It collapses. So the receiving computer sees the interception (whether data, or an attempt to establish the encrypting key).

The snooper cannot get the full key, as any attempt to do so creates corrupted data and alerts the parties. If they get an intercepted fragment of the key while trying to establish one, a new key sequence must be generated to replace the damaged one. If the snooper intercepts a portion of the traffic, the would be able to read it only if clear text (and the receiver would know of the interception). If the traffic was encrypted, they have a tiny piece of encrypted data - but still no key. And the receiver still knows that someone is trying to intercept - time to generate a new key, so that an intercepter cannot collect enough data to work on breaking the encryption. Any new packet will be encrypted with a different key.

Frankly, I don't see how this can be broken. Although, quantum computing in this fashion is strictly Point A-B type computing, not as broad as current computing.

Our understanding of science is always rudimentary of course, so for now this method seems unbreakable, but perhaps in the future it won't be. Apart from that though, (when implemented correctly) this only eliminates "man-in-the-middle" attacks, and does nothing to stop all the other vulnerabilities that we have today. So even if this is a victory it is only a very small one for secure communication.

Lastly, I think it's really commendable that you spend this much time giving well thought answers to peoples questions .

I don't always.

I understand how it works from your description and I've also heard about it before at Uni but what is to stop someone intercepting every packet and therefore causing a DOS attack?

Very true. DoS is always a possibility. One might not intercept and decrypt the information, but can still disrupt it to prevent the other from receiving it.

Hacking/Cracking and blocking are two separate items, though.

Maybe they can replicate the message as early as possible and try and send the packets through multiple routes even if some are less efficient. Not great for performance and it doesn't necessarily save you if you have multiple attackers or they sit somewhere on the line before the messages gets duplicated, but maybe it'd work?

Have you heard the Schrödinger's cat paradox? Basically it states that a cat closed in a steel box can be dead and alive at the same time.
The Heisenberg Uncertainty Principle is so complex. Basically, if you observe, you change the object of observation just by "being there".
The modem can understand if someone observed because the message was changed. For instance if computer A sends "Hello" and the computer B reads "Helol" is because someone intercepted the message. Today's error correction can be used to see it something was changed. Simply hash the message and send the hash. If the hash doesn't apply the message was changed and that the message was not the one that the sender sent. Very simple and very complex.

PS: I work with physical chemistry, Heisenberg Uncertainty Principle is my field.

Wikipedia actually has some good information with reasonable explanations.
http://en.wikipedia.org/wiki/Quantum_cryptography

Pwned!

That's cool, I was done makin' my video anyways.

Ha-ha!

The headline of this story was misleading. The cryptography was not hacked.

Quantum cryptography wasn't hacked, the hardware on which it was implemented was. That's a world of difference.

http://www.tgdaily.com/content/view/39599/108/

Amazing, indeed.

PMSL, I was going to post "I bet someone finds a weakness in this system." Looks like it's already been done. :p

Dude, read above. We've even provided links. I's already been done.