I think it's typically used when there's agreement on the list of nodes participating in the network. (The nodes can agree to change the list of participants, Lamport wrote about it in "Reconfiguring a State Machine".)*
With "blockchain" / proof of work, computing power substitutes for voting power: you pass state transitions by controlling a majority of the compute power rather than a majority of the voting power.
Have you seen "byzantine consensus" used in the second context (with proof of work) also?
(*) When I think of the Byzantine consensus problem, it's when:
- not every node has to vote in each round (so that the system can make progress even if some nodes fail);
- you can authenticate (e.g. with cryptography) that messages come from the appropriate sender (but not whether that sender is acting "honestly");
- the goal is to reach consensus, i.e., if any node concludes that some proposition (i.e. state transition) has passed, no nodes will ever agree on contradictory proposition.
Can you expand on how crypto currencies relate to positive social mobility?
Off-handedly it seems to me it would be the opposite, although I'm admittedly fuzzy on this..
In theory crypto currencies reduce rent-seeking from intermediaries; since much financial rent seeking is established as percentages of an exchange (like a credit card transfer), removing those rents will give bigger net advantages to those transferring large amounts than those transferring small ones.
Not saying removing rent seeking is bad (it's awesome!), but I don't see how that does anything but increase the difficulty for someone with low capital to catch up; rather it should be doing the opposite.
Bringing those who are unbanked into the global financial system is a powerful way to help lift people out of poverty. In many cases, banks are unwilling or unable to serve the poor, so cryptocurrencies could potentially fill the gap. I don't think any current cryptocurrencies will achieve this, but there is some research being done on "stablecoins" which could fit the bill.
Tether?
Im not buying that. If there is a way, someone will do it. This actually seems like a huge vulnerability to me. Especially when we are talking about specialized blockchains where the participation isnt every internet connected person in the world. How do you prevent that from happening?
At times the leading BTC mining pool has controlled greater than 50% of the nodes. Would this not be enough to alter the ledger?
But you can't alter the core protocol or fundamental network rules. If you do, the other nodes will ignore you.
Somehow "the other nodes" have reached consensus about what protocols or rules to follow, and this is where we end up back at human governance.
I suggest listening to this Tim Ferris podcast with Nick Szabo: http://tim.blog/2017/06/04/nick-szabo/
The entire idea is that no arbiter is truly neutral, no third party is truly trustworthy. Block chain is the onset of FAT protocols and trustful computing.
If the poor of the world can understand the social mobility that crypto currency affords them, there will be no stopping it, in my opinion.