Behind the First Secure Quantum Crypto Network

schliz writes "Researchers behind the world's largest quantum encrypted network said the technology could secure business networks inside six years. The prototype Quantum Key Distribution network was built by the Secure Communication Based On Quantum Cryptography (SECOQC) group last year. It is described in a journal paper published by the Institute of Physics this week, which includes details on how it is based on the trusted-repeater paradigm."

Excuse me, but...

[kvezach]

... what's the point of this network? The weakness of current crypto isn't that someone will break it to decrypt in feasible time, but rather what happens outside of the crypto itself. No perfectly secure quantum network can stop worms or social engineering attacks, and as far as cryptographic algorithms themselves go, AES-256 and RSA-3072 is strong enough.

Now, if suddenly everybody had a quantum computer that could break RSA in polytime, there might be a point to this, but they don't, so there isn't - not that I can see.

Bunch of new problems with quantum cryptography

[getuid()]

From what I've been told (I am a physics major, but I don't work in quantum cryptography as my main activity), there's a bunch of other weaknesses inherent to quantum encryption methods.

For example, qubits are mostly transfered through some optical medium. At the receiving end, at some point, they are detected in one way or the other. "Detecting" means they alter the state of the detector in a measurable way. And there are some ideas (maybe even implementations?) of attacks that try to measure the alteration of the detector immediately after the detection, for example by probing with a laser pulse that follows the qubit pulse.

Now due to some limitations of the physics of light pulses, this is something that, if implemented, is very difficult to defend against, since the light always goes both ways. It is also a kind of attack that could not be implemented against "classic" information transmission channels...
 
...I really find it interesting that every new technology seems to have its inherent weaknisses at one spot or the other -- kinda feels comfortable to know that "There is no silver bullet" [wikipedia.org] still holds... :-)

Re:You have said this before, multiple times

[gweihir]

And if you look at them, one is an original post and the other two are replies. Knowing how to read is more than just knowing the letters.

Re:Bunch of new problems with quantum cryptography

[Anonymous Coward]

Actually, light does not necessarily go both ways: you can have it go only one way using an "isolator". These are cheap fibre components that are used very commonly. Of course there are some implementation weaknesses in quantum cryptogrophy, an article that examines various protocols is: http://arxiv.org/abs/0802.4155

Re:Excuse me, but...

[Anonymous Coward]

AES-192 and AES-256 are weaker than AES-128:

https://cryptolux.uni.lu/mediawiki/uploads/1/1a/Aes-192-256.pdf