Quantum mechanics creates location-based cryptography

[Forkboy]

Imagine a form of encrypted communication so secure that it's physically impossible to access it unless you're actually at the location where you're supposed to hear it. Quantum mechanics makes location-based cryptography possible - without any pesky codes or keys.

The basic idea is simple - create an encrypted communication where your actual physical location is the only key required to gain access to the hidden information. It would eliminate any need to create and store decryption keys, which is disproportionately the most complex and time-intensive task in cryptography. You could encrypt a secure line so that the only people who could ever hear would have to be at, say, two secure military bases, eliminating any chance of someone listening in from a third location.

And now computer scientists at UCLA have figured out how to do it. The big problem holding back location-based cryptography was that triangulation, the classical method of verifying the receiver's location is the correct one, can be forged if enemies work together to provide just the right combination of wrong information. But that's just classical physics - quantum mechanics has that problem solved. The solution lies in the no-cloning theorem, an outgrowth of the uncertainty principle that basically states it's impossible to create an exact replica of a quantum state.

This means that, when the secure transmitter sends out multiple quantum bits, or qubits, the intended receiver is the only device that can verify the information and confirm they are who they say they are. If an adversary was trying to listen in, they'd still need multiple transmitters to mimic the supposed location, but that's now physically impossible because the first adversary would need to both store the qubit's state and send it on to the next confederate, and quantum mechanics says that's impossible.

http://io9.com/5597728/quantum-mechanics-creates-location+based-cryptography

[patrice]

1. Where can I get one of these?

Thanks Forkboy!

:hi:

[xchrom]

2. I wish I understood what you just said.

It's not dirty is it?

I'll be bummed if I don't understand it
And it's dirty.

[dtexdem]

3. Can you hear me now?

Then how about here?

;-)

[Jim__]

4. "The basic idea is simple ..."

OK. Can someone explain the basic idea to me? I know what triangulation is, but I don't understand how this works. The sender sends out some qubits and they can't be both stored and cloned.

Is the fact that it's being transmitted to 2 different receivers integral to this process? Does it have to be transmitted to 2 different receivers due to the triangulation? How do the non-clonable qubits fit into this. The first receiver receives the qubits. But, since they can't be cloned, I assume the sender cannot retransmit them.

I don't get it.

[TheMadMonk]

5. Two or more transmitters can be modulated in such a way as to appear at a distance...

...to be one transmitter in between. Triangulation takes a bearing on a signal, to be sure if it's coming from the right direction. Two bearings can be plotted on a map and their intersection point should be the transmitter's location. A spoofed signal causes the triangulating receivers to mistakenly "average" the signals.

Quantum cryptography relies on signals that are destroyed when they are read. To spoof location based quantum cryptograpghy, you would have to be able to recreate the original signal at least twice, transmit it to your two separate spoof transmitters, somehow retransmit without destroying the quantum information and do it in such a way that two quantum "packets" become one.

[Jim__]

6. Thanks. That helps.