Quote from: _mr_e on July 05, 2014, 07:49:01 PM

Quote from: Peter R on July 05, 2014, 07:43:36 PM

Quote from: Luke32 on July 05, 2014, 06:38:29 PM

Quote from: justusranvier on July 05, 2014, 11:27:15 AM

PoS coins use the number of coins held as the basis for their signalling system. Since coins have an exchange rate, they obviously do not fulfill the criteria of having no value, either practical or intellectual. Thus PoS is not an viable mechanism for honest signalling.

The criterion of having no value is a theoretically sound one for proof of work systems. I am not convinced it's correct to apply this criterion to proof of stake systems the way you did it, because PoS and PoW solve the distributed consensus problem in a different manner. Let me try to explain:

What's the reason behind the criterion that the calculations in a PoW system must have no value (either practical or intellectual)? This simply to increase the cost for an outsider to successfully attack the system, right? To ensure that "telling the truth" is more profitable than "lying".

With PoS, the signalling system is indeed based on coins which have value. This means outsiders (those who don't own coins) can't influence the signalling system. The coins however only have value as long as the system functions as it should (the same is of course true for PoW systems). I therefore think this system also ensures that "telling the truth" (which makes the system functions as it should) is more profitable than "lying", and could thus be a viable mechanism for honest signalling.

No. The "signalling system" for PoS is based on coins which have value now or which had value at some point in the past. An attacker can use coins that have already been legitimately spent (i.e., he has nothing at stake) to attempt to "re-write history" in his favour, thereby creating a new "best" chain where his coins haven't been spent. This is the "nothing-at-stake" or "history-rewrite" problem¹.

Before one can even intelligently debate PoS, one must at least review the original proof-of-stake thread here, the many highly-refined thoughts by DeathAndTaxes (CEO of BitSimple) here, and perhaps Andytoshi's work in Section 5 of this document. One must understand the nothing-at-stake problem.

What I think we need, and I was talking with Chris Wilmer about this a few months ago, is to launch a peer-reviewed journal J Bitcoin, to help put an end to derpfests like these tireless PoS debates. This way, we can point to a well-written article, reviewed by experts in the field, to both disseminate the work of our community more effectively and make the true state of knowledge more clear. I would donate 1 BTC to such a cause if we had a credible plan to make the journal happen.

¹Current PoS coins get around this problem, for example, by having the developers sign blocks as valid (Peercoin) or by introducing regular blockchain checkpoints into the code (Nxt). In other words, these PoS coins are not decentralized.

Nxt does not suffer from the nothing at stake issue and I'm not sure that it still uses checkpoints either.

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no, nxt doesnt use checkpoints anymore.