The secure key has a unique serial number allocated to it which is only known by the bank. The key has a clock in it which is synchronized with the clock on the bank's computers before it is sent out. You set the PIN on the secure key which is only known by you.
I guess the internal clock must only be accurate to human scale time intervals.
This is a video series by Steve Gordon and is well done. I wanted to understand the cryptology underlying Bitcoin and found this series after fishing around on YouTube. For my purposes I started off with the 11th lecture in the series that details the number theory required to understand encryption. I have embedded the 11th lecture in the series below and it starts with lecture 11 but it is only one in the CS322 lecture series and the series is probably better viewed by going direct to YouTube. Fore an easy and quick summary and numeric example see: RSA Code Made Easy
Personality traits displayed demonstrated in regards "awards" and "fame" are very reminiscent of Feynman. I don't admire sports figures, presidents or musicians. I admire people like this who can scoop up bits and pieces of the universe and form them into something new. Most inventions are so derivative as to be barely worth mention. Very rarely as in this case something totally new in its application in created. This is one of those cases. If he does not receive the Nobel Prize it should be a shock.