Encryption and HUGE numbers - Numberphile
This video features Dr James Grime (http://singingbanana.com/). Message from James: "Thanks to Dr Chris Hughes of the University of York who showed me how to find the RSA public key from my browser, and showed me how awesome they look when you print them out."
The brown paper from this video can be purchased on ebay: http://www.ebay.co.uk/itm/221164184385
Thanks to Drew Mokris for the animation: http://www.spinnerdisc.com/
Numberphile on Facebook: http://www.facebook.com/numberphile
Numberphile tweets: https://twitter.com/numberphile
Videos by Brady Haran