Hackers Eavesdrop On Quantum Crypto With Lasers

Martin Hellman writes "According to an article in Nature magazine, quantum hackers have performed the first 'invisible' attack on two commercial quantum cryptographic systems. By using lasers on the systems — which use quantum states of light to encrypt information for transmission —' they have fully cracked their encryption keys, yet left no trace of the hack.'"

Comments

Re:Commercial Systems

[PseudonymousBraveguy]

Quantum cryptography is academic at this point. It is not as strong as old fashioned cryptography (like AES) and is much more expensive. Then I realized that there is no reason that someone can't use both.

Quantum crypto (at this point) is a key exchange mechanism. Thus, it doesn't compare to AES at all. You HAVE to use quantum crypto together with a classical exncryption algorithm. However, if you use quantom crypto you care about 100% theoretical security. Else you would simply use DH or any other well-known classical key exchange. And if you care about 100% theoretical security, there is no alternative to OTP.

Re:Commercial Systems

[julesh]

Except that to be able to use quantum crypto at all, you need to provide a physical way to pass the quantum state. And with that requirement, why won't you just pass the key the good old fashioned way? Strictly more secure, and much cheaper.

More secure? Hardly. All you have to do is eavesdrop on the key exchange and you have the key. In a real world scenario, typically this means bribing a few security guards, breaking into one of the communicators' homes or offices and retrieving the key from their computer, or intercepting a message sent over a physical line, probably encrypted via a non-100%-reliable cryptographic system, with the (at least) theoretical possibility that the encryption on the key exchange can be broken.

In a properly implemented quantum crypto system, this is theoretically impossible: the key passes directly from one endpoint to the other, and any interference between the two is easily detectable. It isn't stored for longer than the message takes to be sent, so breaking in to retrieve it is impractical. Done properly, the quantum crypto system is as secure as it is possible to be. As it happens, the system here was not done properly; it failed to detect interference on the line (and as ability to detect interference is, essentially, the point of quantum crypto, this is bad news).

Re:pwned

[maxwell demon]

Well, there are several points here:

• Every cryptographic security is only up to possible bugs in the implementation (remember the Debian ssh problem?), so exactly 100% security is impossible. However, one difference betweeen the classical and quantum case is that in the quantum case any possible exploit has to be "online" (i.e. you have to actually intercept the actual sent message and manage to manipulate the receiving system), while for classical key exchange the breaking can also be after the fact (i.e. if all you want is the exchanged information, you can passively record all data and then try to break it afterwards). This means that
  1. all communications performed before that exploit was found remains secure (unlike classical protocols where you only need the recorded data to apply any exploit), and
  2. since the attacker has to manipulate the systems during operation, as soon the exploit is known you can take additional measures in order to detect it (e.g. in this case, I think it should be quite easy to detect a relatively strong laser which is continuously shining at the receiving device), thus detecting whether someone tries to exploit it (unlike classical systems, where you have no clue if someone tries to attack your cryptographic system). That is, instead of replacing your whole cryptographic infrastructure (which may be expensive), you can simply add detectors for the manipulation needed for the exploit, so that you only transmit confidential information in case the exploit isn't applied.
• As the article mentions, the commercial systems add the quantum cryptography on top of the classical cryptography. So if the quantum cryptography is broken, you still have the security of the classical system. On the other hand, if the classical system used is broken (be it because the underlying cryptographic scheme is broken, or be it by exploiting a bug in the specific implementation) then you still have the security of the quantum cryptography.

Article Makes No Sense

[SeekerDarksteel]

The article is either missing massive details or these researchers are vastly overstating the power of their technique. The entire _point_ of quantum key exchange is that if Eve intercepts the signal she cannot tell if she read a 0 or a 1 because she does not know which basis the 0 or 1 was generated in. Even IF Eve passed a 1 along every time she read a 1, when Alice and Bob go to do the basis comparison over the standard channel they will notice errors because Eve read the signal in the wrong basis and passed along an incorrect value.

I've tried reading the actual journal paper, but unfortunately they just seem to handwave this problem away. Maybe there's a reason they can, but its sure as hell not explained as far as I can see unless they're assuming Eve has also compromised the classical channel as well as the quantum channel.

Re:pwned

[WED Fan]

Why the GP was modded troll is beyond me. This is a "huge kick in the balls". Isn't the point of QC to make it easy to detect if someone has even listened in, let alone broken anything? I'd have to say that what it means is the current implementation of QC is an epic fail. Back to the old drawing board.

Re:Why 'hackers' and not 'researchers'?

[Vadim Makarov]

with the manufacturer's full approval to boot

I'm not sure the manufacturers would approve the existence of our lab if they could dictate it. Thankfully we are independent and need not seek their approval. The manufacturers did appreciate responsible disclosure, though. I don't know how this hacking affects their business in the short term (may as well be detrimental to sales), even though it is surely good for business in the long term as it leads to more secure systems.