[ISN] Location-based quantum crypto now possible, boffins say

http://www.theregister.co.uk/2010/08/03/location_based_crypto_breakthru/

By Dan Goodin in San Francisco
The Register
3rd August 2010

Researchers say they have devised a foolproof way to encrypt messages 
that can be unlocked only by a recipient physically located in a 
specific place, solving a problem that has vexed cryptographers for 
years.

The technique for position-based quantum cryptography is scheduled to be 
presented at the 2010 IEEE Symposium on Foundations of Computer Science 
in October. It makes it theoretically possible for people to securely 
encrypt and decrypt messages without the use of pre-shared keys. 
Instead, the messages would be encrypted using keys based on a 
recipient's physical presence at a secure facility.

"The aim of position-based cryptography is to use the geographical 
position of a party as its only credential," the researchers wrote in 
their paper. "This has interesting applications, e.g., it enables two 
military bases to talk to each other over insecure (i.e., neither 
private nor authenticated) channels and without having any pre-shared 
key, with the guarantee that only parties within the bases learn the 
content of the conversation."

The technique builds off of previously reported research that suggested 
position-based crypto was impossible to pull off against multiple 
colluding adversaries scattered in different places. The researchers 
solved this problem by devising a way to use quantum mechanics to 
determine a party's location that can't be spoofed.

[...]


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