posted on Aug, 8 2006 @ 01:40 PM
Originally posted by northwolf
Some Finnish "specialist" said something about max 2m, and the start keys should be in action atleast with Finnish version... so a 3m buffer zone
around customs booths should be enough...
That's probably not far from wrong. You couldn't interrogate from 2M, but if you had it in an interrogator that was real close, you might be able to
snipe the return signal out of the noise up to 4 or 5 feet away. You'd have to be pretty good.
It's not possible to receive any return from the passport in the far field, so you would have to be closer than 3.5M at best case. Even then,
there's diddley for signal until you're at about half that. So, yeah, within about 2M you're in the "knee" where the signal starts being high
enough to read.
You know, we solved something sort of analogous to this by having the encryption keys stored in a main server. The readers had to use other keys to
get the encrypted data from the tag but didn't inherently know how to unscramble it.
The reader sent encrypted reader bonafides to the server, along with encrypted tag bonafides (which the reader couldn't interpret either), the
reader operator's biometrics (a pair of fingerprints and a day code) and a GPS address of the reader. If everything looked ok, and the operator and
locale was valid, then the server would return the private half of a session key that unlocked the data from the tag. It happened a lot faster than it
sounds. But fake readers, fake tags, bogus operators, no one reporting the reader theft, faking GPS coordinates, it would have been really really
tough to get the unencrypted data. You could have intercepted it until you turned blue but you wouldn't have gotten the data, just jumble.
At the end of the session, the server would send the public half of the next random key to the tag. The tag never had the same encryption keys for
more than one session so even if you caught the key during the read it wouldn't have done you any good.