Second lecture of the Bitcoin and cryptocurrency technologies online course.

For the accompanying textbook, including the free draft version, see: bitcoinbook.cs.princeton.edu/

In this lecture (click the time to jump to the section):
* Centralization vs. decentralization 1:12
* Distributed consensus 4:45
* Consensus without identity: the block chain 17:46
* Incentives and proof of work 35:43
* Putting it all together 55:39