Here’s the up-to-date graph of hashing power distributed by mining pools (that I wasn’t able to find in class Monday):
https://blockchain.info/pools?timespan=4days
Looking at the current results for the past for days, more than 50% of the hashing power appears to be held by just three mining pools: F2Pool (20%), BitFury (17%), and AntPool (17%). Each of these has around 75 PH/s (one peta-hash means 1015 computations of the bitcoin block hashing function, which actually involves two computations of SHA-256).
We’ll talk about mining a lot more in the coming weeks to get a good understanding of what this means technically, as well as the implications for the blockchain.