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ESA's Optical Ground Station (OGS), which served as the receiving station for a recent quantum encryption experiment, is located at the Observatorio del Teide on Tenerife.
Long-distance relay proves concept of foolproof security using entangled photons

A group of European scientists succeeded in beaming an encryption code based on photons across about 90 miles of ocean. The experiment took place recently in the Canary Islands, from a light source on the island of La Palma to a receiving station on nearby Tenerife. The researchers published their exploits in this month's issue of the academic journal Nature Physics.

 

According to the European Space Agency, which funded the study, the experiment allows ESA to move closer to harnessing entanglement as a means of "communicating with satellites with total security."

 

Entanglement is an unusual property of quantum mechanics used to describe the manner in which photons naturally interact with each other. Using a non-linear process called Spontaneous Parametric Down Conversion (SPDC), it is even possible to directly create pairs of entangled photons. These entangled photons lend themselves to encryption applications because of their unique linkage. If one photon is exposed to a third particle, both of the paired photons will change their state instantaneously -- even though one of the photons is physically separated from its mate.

 

The degree of change in the state of the paired photons is completely random and unpredictable, according to ESA, theoretically foiling any attempt by a third party to decode the message without actually intercepting the quantum encryption key. However, the very act of detecting the photons would change the state of the photon pair, betraying the presence of an eavesdropper. "These changes would be obvious to the legitimate receiving station and the presence of the eavesdropper would be instantly detected," ESA wrote in its official announcement of the experiment's success.  "Such behavior has the potential to allow messages to be swapped with complete confidence."

 

Prior to the inter-island experiment, it was not known whether entanglement would be adversely affected when the beam of entangled photons was transmitted through the atmosphere over a considerable distance. The favorable results of the experiment have given the space agency confidence that entanglement does not decay over long distances, indicating that quantum encryption can be harnessed for securing satellite communications.

Possible applications for the unbreakable code might include transmissions of financial data between banks, military communications and even the distribution of feature films, according to ESA officials.

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Can you say Denial-of-service attack?
By leidegre on 6/13/2007 6:24:26 AM , Rating: 2
If the mere observation of encrypted information changes the state, how would this change with respect to interference and/or possibly a DoS attack. If communication is completely cut, how is this a better alternative? It doesn't seem to mention security itself, just that it would be secure if it would succeed...




RE: Can you say Denial-of-service attack?
By hellokeith on 6/13/2007 7:29:40 AM , Rating: 2
Even internet DoS attacks are temporary at most. The very best a hacker interfering with satellites could hope for is not getting caught by law enforcement within hours of the attack and at worst having bombs dropped on him.


By leidegre on 6/13/2007 8:47:05 AM , Rating: 2
Do you really think it's that simple to pin point a device that is messing with a quantum stream?

Then, on the other hand, that type of equipment might be complex, and infinte expensive as well...


By jak3676 on 6/13/2007 8:48:06 AM , Rating: 2
Yes, the average newbie kind of attack would be quickly detected and responded to. But if this is going to be the future of military and state level encryption, then there will always be plenty of orginizations that may not care about getting caught. At the nation-state level of computer network attack and exploitation the orinizations aren't really resouce limited, its just a matter of how much risk you are willing to take.


RE: Can you say Denial-of-service attack?
By masher2 (blog) on 6/13/2007 9:26:09 AM , Rating: 4
> "If communication is completely cut, how is this a better alternative? "

Because this ensures that, if you receive a message, it hasn't been intercepted, altered, or tampered with in any way.

We already have an unbreakable encryption scheme-- the one-time pad. But its not practical to use in most cases due to the difficulty with exchanging keys. Using quantum encryption, sender and receiver can exchange a key, and be assured that no one else has read it.


RE: Can you say Denial-of-service attack?
By FITCamaro on 6/13/07, Rating: 0
RE: Can you say Denial-of-service attack?
By masher2 (blog) on 6/13/2007 9:38:53 AM , Rating: 4
You wouldn't neccesarily receive the message...quantum encryption uses transmission schemes that are as vulnerable to interference and interception as normal ones. It's just not vulnerable to surreptitious eavesdropping. If an eavesdropper exists, he will be detected.


RE: Can you say Denial-of-service attack?
By FITCamaro on 6/13/07, Rating: 0
RE: Can you say Denial-of-service attack?
By masher2 (blog) on 6/13/2007 10:44:45 AM , Rating: 2
> "...because someone tried to intercept it, that doesn't mean it won't be received."

But in quantum encryption, thats just what it does mean. If you intercept a message, you influence its state. And that means the receiver doesn't receive the same state-- they receive something else entirely. That's why quantum key exchange is secure.


By leidegre on 6/13/2007 11:20:46 AM , Rating: 2
And this exactly why I'm concernd with the DoS thing, surly there must be ways make sure the stream is always tampered with, and thus useless, like radar jamming. Quantum jamming ftw! Or is it just highly-unlikly that it would occur/be possible...


RE: Can you say Denial-of-service attack?
By Deekity on 6/13/2007 2:16:02 PM , Rating: 3
Right - i'm sure people trying to subvert intelligence communications would settle for disrupting transmissions entirely since they can't read/intercept them.


By hubajube on 6/13/2007 5:06:19 PM , Rating: 3
quote:
Right - i'm sure people trying to subvert intelligence communications would settle for disrupting transmissions entirely since they can't read/intercept them.
Why not? That type of activity is done already. If someone can't decrypt a transmission but they know where it's going they just may (and have) jam it to prevent it from reaching its destination.


By InsaneGain on 6/13/2007 6:32:47 PM , Rating: 2
From what I understand, other than the entanglement, there is no physical connection of any kind made between the two entangled particles. One particle's state simply determines the other particle's state instantly. How would someone disrupt or listen in on something that emits no fields or energy of any kind? I would think that a listener would have to have access to a particle that was also influenced by one of the entangled particles.


By namechamps on 6/14/2007 9:26:55 AM , Rating: 2
So you are going to block one photon of light that only travels LOS between the sender and receiver?

Essentially you would need to be perfectly positioned between the sender and receiver. In case of a ground station and sat you likely would need to be hovering over the ground station in the sender's airspace.

Even without QE interception is very difficult for LOS technologies. Difficult is not good enough. If you transmit a key in the clear and you are 99.99999999999999% certain nobody intercepted the key is that good enough for nuclear launch codes? With QE if the key is intercepted then it is changed and therefore invalid. You would throw away the key, remove/arrest/destroy the eavesdropper then transmit again. Once you get a good transfer you know with absolute 100% certainty that only the sender and receiver have the key.

DOS attacks on LOS technology with or without QE are virtually impossible.


Seems like it shouldn't work...
By ralith on 6/13/2007 8:35:44 AM , Rating: 2
quote:
If one photon is exposed to a third particle, both of the paired photons will change their state instantaneously -- even though one of the photons is physically separated from its mate.

Given that information in the quote how the heck do you transmit the photons through anything other than vacuum without changing their state? Seems to me that an atom is a particle. Maybe it has to interact with a photon to change state? Man I need to read up on this stuff. Anyone know any good link besides the wikipedia link?




RE: Seems like it shouldn't work...
By Moishe on 6/13/2007 9:04:32 AM , Rating: 2
I think the general idea in client/server app terms is:

Photon #1 (server)

Photon #2 (client)

There is no "transmission" of anything. If you change the state of #1, then #2 automatically and instantly reflects that change.

So if you're using it like data, you simply set the server photons to "be" the 1's and 0's for "Transformers 2" and the client (at the theater) instantly has the Transformers 2 movie on site.

This is simplistic and I'm not up on all this stuff, but this is my understanding of how it works. Correct me if I'm wrong.


RE: Seems like it shouldn't work...
By PaxtonFettel on 6/13/2007 9:34:00 AM , Rating: 2
That sounds about right, I'm really rusty on this stuff.
But it can't really be instant can it? That would mean transmitting information at greater than lightspeed, which shouldn't be possible (yet).


By masher2 (blog) on 6/13/2007 9:40:53 AM , Rating: 3
> "But it can't really be instant can it? "

It's instantaneous-- but it doesn't violate relativity, as you cannot transmit information via quantum entanglement alone.


RE: Seems like it shouldn't work...
By masher2 (blog) on 6/13/2007 9:35:13 AM , Rating: 3
> "There is no "transmission" of anything"

Even with entanglement, you still need to transmit one of the entangled particles to the remote location. As of now, we don't know any method of entangling two spatially-disparate particles.

One entangled, now, the particles can be separated by any distance, and information exchanged by changing the state of one particle, then reading the state of the other.


RE: Seems like it shouldn't work...
By slashbinslashbash on 6/13/2007 11:08:57 AM , Rating: 2
And this changed state happens instantaneously, no matter what the distance? How is that not breaking relativity, exactly? Just because the entangled particles had to be created in the same place and one of then transported away by slower-than-light means?