Quote from: monsterer on September 16, 2015, 09:51:26 PM

Quote from: r0ach on September 16, 2015, 09:25:57 PM

Delegated proof of work, which Bitcoin is, doesn't. It's no more fault tolerant than DPoS.

Hashcash POW is subject to sybil due to ASICs, this is clearly something that satoshi did not foresee, I agree. However, that does not rule out all other types of POW - there exists a near idealised POW in which one CPU really is one vote.

DPOS has no white paper and has not been proven to solve the byzantine problem, much like most other consensus designs.

PoW doesn't require 1C1V. It only requires that (or more precisely requires that no actor have disproportionate voting power) to converge in the manner stated in the paper. Nevertheless it will still eventually converge with weaker assumptions on rate.

Even if you can sybil at the level of miners or pools, you still can't sybil at the level of hashes.

So the pools in China could fork the chain starting 20 or 30 blocks back and double spend. But it would cost them 20-30 blocks worth of hashes to do it. Trying to do this say a year back, while theoretically possible since they have 50+% of the hash rate, would not be feasible. Even if it were, and they did it, they certainly couldn't keep doing that repeatedly because it would cost infinite energy. Eventually they will run out of money and need to let the chain progress forward.

Thus there will still eventually (and remember, even if the ideal 1C1V case PoW doesn't observe a deadline) be an unambiguous longest chain, and therefore a consensus, although it may be a slow and messy one.

By contrast, in PoS with a sufficient portion of old stake, you can create as many versions of the chain as you want without incurring this kind of cost. DPoS doesn't matter here because you can create new chains with different election results, and the proceed as above. (You can infer a cost if you view PoS as a form of PoW where creating chains is the PoW, but this doesn't help the argument.)

The only defense is "everybody knows which is the right chain" which is not a system reaching consensus, it is people forming it.