The nothing-at-stake issue manifests itself in numerous different ways. For example in PoS but not in DPoS, it can manifest in a stake grinding attack, which converts PoS into PoW. So you've achieved nothing with PoS. Checkpoints don't help to stop stake-enabled malfeasance in real-time, i.e. there is nothing-at-stake to attempt attacks in between checkpoints. There are various schemes that purport to deal with certain attacks and we even have NEM's Proof-of-Importance which obfuscates that it is really attackable by nothing-at-stake. To respond to each of these with details on the different varieties of nothing-at-stake vulnerabilities for every hyped NAOD (nonsense algorithm of the day), is more time than I can waste right now. But if you read my rebuttal of Dan Larimer linked below, you will get some flavor for the fact that it is indeed possible to find egregious, insoluble flaws in all these PoS variants. In short, none of the consensus systems (including PoW) invented thus far are robust enough. I wrote about this yesterday:
https://steemit.com/blockchain/@anonymint/future-of-decentralized-currency-is-not-bitcoin
https://medium.com/@shelby_78386/future-of-decentralized-currency-is-not-bitcoin-eec2e9c39a0a
Both PoS and DPoS have the nothing-at-stake flaw that it can be in some scenarios more liquid (on a time opportunity cost basis) to attack and short the coin, than it can be to protect one's stake for the long-term investment. Thus the stake is really nothing-at-stake. Whereas, for "the one chain to rule them" on non-repurposable ASICs, the PoW mining farms have at stake their huge sunk costs and long-term leases which they can't recover with shorting and overt attacking. However, for lesser PoW chains and those without an ASIC, they can in theory be attacked by renting hashrate and/or botnets. This is all covered in great detail in my whitepaper which will hopefully be released within Q1 2017.
Note even Dan Larimer could not refute my summary of attacks on his DPoS. Make sure you click that link and get a little bit of the flavor of the deep level of inspection of issues you will get with my coming whitepaper.
IOHK and Charles Hoskinson did not solve the problem that the stake concentrates in a power vacuum and that 51% of the stake can still do malfeasance.
...However, these "wolverine federated systems in an illusory democratic sheepskin" are more computationally efficient than systems which employ proof-of-work.
IOHK has proved security for a PoS system, but the assumption remains that the majority of the stake is not colluding to violate the Nash equilibrium and a majority of the stake remain online at all times. I don't see what IOHK's PoS accomplishes which isn't already accomplished by DPoS? Is it more objective w.r.t. to violations of Nash equilibrium since in DPoS the majority of the stake can be offline so can't observe first-hand any violations? DPoS is presumably provably secure if a majority of the delegates adhere to the Nash equilibrium.
So in summary, we can hide "wolverine federated systems in an illusory democratic sheepskin" and gain computational efficiency. But the security problems (or more realistically the economic centralization problem since large stake holders need insidious means as there isn't sufficient shorting liquidity for them to scorch their earth) shift to the power vacuum of political economics and the inviolable power-law distribution of wealth (beget by economies-of-scale). Yet Satoshi's design also has these centralization problems due to the power vacuum of political economics and the inviolable power-law distribution of wealth (beget by economies-of-scale).
Will anyone find another class of solution which provides long-term stable resistance to the centralization inherent in the power vacuum of political economics and the inviolable power-law distribution of wealth (beget by economies-of-scale)? Is (D)PoS already more realistically resistant to insidious effects of centralization of vested interests "stake" than Satoshi's design?
This is the Holy Grail we seek because centralized ecosystems don't scale due to the stifling politics and vested interests. In my opinion (which is probably an analysis many others share), this is what is holding back Bitcoin lately.
IOHK has proved security for a PoS system, but the assumption remains that the majority of the stake is not colluding to violate the Nash equilibrium and a majority of the stake remain online at all times. I don't see what IOHK's PoS accomplishes which isn't already accomplished by DPoS? Is it more objective w.r.t. to violations of Nash equilibrium since in DPoS the majority of the stake can be offline so can't observe first-hand any violations? DPoS is presumably provably secure if a majority of the delegates adhere to the Nash equilibrium.
So in summary, we can hide "wolverine federated systems in an illusory democratic sheepskin" and gain computational efficiency. But the security problems (or more realistically the economic centralization problem since large stake holders need insidious means as there isn't sufficient shorting liquidity for them to scorch their earth) shift to the power vacuum of political economics and the inviolable power-law distribution of wealth (beget by economies-of-scale). Yet Satoshi's design also has these centralization problems due to the power vacuum of political economics and the inviolable power-law distribution of wealth (beget by economies-of-scale).
Will anyone find another class of solution which provides long-term stable resistance to the centralization inherent in the power vacuum of political economics and the inviolable power-law distribution of wealth (beget by economies-of-scale)? Is (D)PoS already more realistically resistant to insidious effects of centralization of vested interests "stake" than Satoshi's design?
This is the Holy Grail we seek because centralized ecosystems don't scale due to the stifling politics and vested interests. In my opinion (which is probably an analysis many others share), this is what is holding back Bitcoin lately.
Sorry I don't have time to waste arguing on the forum. It is time to get something accomplished, which I can't do it I am going back and forth here.
If any of you have something important to debate, write a white paper. Do some deep research. Write a comprehensive document. All this n00bs pontification from their armchairs is actually spreading disinformation.
I am not claiming kiklo is a n00b, but he is not telling you everything he knows when he replies. He is just telling you the part that makes PoS look favorable.
kiklo is correct that in theory the lesser PoW chains and especially those without ASICs in theory need checkpoints, but that doesn't even protect them from rented hashrate attacks. However his point does not apply to Bitcoin. Bitcoin has checkpoints to be extremely paranoid such as if for example there was breakage of SHA256 such as a quantum computer attack such as the one described at the end of Iota's Tangle white paper.
. From what u wrote its clear u misunderstood how proof of stake works. 