In the paper <i>Reconsidering Physical Key Secrecy:
Teleduplication via Optical Decoding</i> (<a href="http:&#x2F;&#x2F;vision.ucsd.edu&#x2F;~blaxton&#x2F;pagePapers&#x2F;laxton_wang_savage_ccs2008.pdf" rel="nofollow">http:&#x2F;&#x2F;vision.ucsd.edu&#x2F;~blaxton&#x2F;pagePapers&#x2F;laxton_wang_savag...</a>) they manage to decode a key from 200 feet away. Pretty cool stuff.