Re: [bitcoin-dev] Opinion on proof of stake in future

[Billy Tetrud <billy.tetrud@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 10126 bytes --]

I think there is a lot of misinformation and bias against Proof of Stake.
Yes there have been lots of shady coins that use insecure PoS mechanisms.
Yes there have been massive issues with distribution of PoS coins (of
course there have also been massive issues with PoW coins as well).
However, I want to remind everyone that there is a difference between
"proved to be impossible" and "have not achieved recognized success yet".
Most of the arguments levied against PoS are out of date or rely on
unproven assumptions or extrapolation from the analysis of a particular PoS
system. I certainly don't think we should experiment with bitcoin by
switching to PoS, but from my research, it seems very likely that there is
a proof of stake consensus protocol we could build that has substantially
higher security (cost / capital required to execute an attack) while at the
same time costing far less resources (which do translate to fees on the
network) *without* compromising any of the critical security properties
bitcoin relies on. I think the critical piece of this is the disagreements
around hardcoded checkpoints, which is a critical piece solving attacks
that could be levied on a PoS chain, and how that does (or doesn't) affect
the security model.

@Eric Your proof of stake fallacy seems to be saying that PoS is worse when
a 51% attack happens. While I agree, I think that line of thinking omits
important facts:
* The capital required to 51% attack a PoS chain can be made substantially
greater than on a PoS chain.
* The capital the attacker stands to lose can be substantially greater as
well if the attack is successful.
* The effectiveness of paying miners to raise the honest fraction of miners
above 50% may be quite bad.
* Allowing a 51% attack is already unacceptable. It should be considered
whether what happens in the case of a 51% may not be significantly
different. The currency would likely be critically damaged in a 51% attack
regardless of consensus mechanism.

> Proof-of-stake tends towards oligopolistic control

People repeat this often, but the facts support this. There is no
centralization pressure in any proof of stake mechanism that I'm aware of.
IE if you have 10 times as much coin that you use to mint blocks, you
should expect to earn 10x as much minting revenue - not more than 10x. By
contrast, proof of work does in fact have clear centralization pressure -
this is not disputed. Our goal in relation to that is to ensure that the
centralization pressure remains insignifiant. Proof of work also clearly
has a lot more barriers to entry than any proof of stake system does. Both
of these mean the tendency towards oligopolistic control is worse for PoW.

> Energy usage, in-and-of-itself, is nothing to be ashamed of!!

I certainly agree. Bitcoin's energy usage at the moment is I think quite
warranted. However, the question is: can we do substantially better. I
think if we can, we probably should... eventually.

> Proof of Stake is only resilient to ⅓ of the network demonstrating a
Byzantine Fault, whilst Proof of Work is resilient up to the ½ threshold

I see no mention of this in the pos.pdf
<https://download.wpsoftware.net/bitcoin/pos.pdf> you linked to. I'm not
aware of any proof that *all *PoS systems have a failure threshold of 1/3.
I know that staking systems like Casper do in fact have that 1/3
requirement. However there are PoS designs that should exceed that up to
nearly 50% as far as I'm aware. Proof of work is not in fact resilient up
to the 1/2 threshold in the way you would think. IE, if 100% of miners are
currently honest and have a collective 100 exahashes/s hashpower, an
attacker does not need to obtain 100 exahashes/s, but actually only needs
to accumulate 50 exahashes/s. This is because as the attacker accumulates
hashpower, it drives honest miners out of the market as the difficulty
increases to beyond what is economically sustainable. Also, its been shown
that the best proof of work can do is require an attacker to obtain 33% of
the hashpower because of the selfish mining attack
<https://github.com/fresheneesz/quantificationOfConsensusProtocolSecurity#the-selfish-economic-attack>
discussed
in depth in this paper: https://arxiv.org/abs/1311.0243. Together, both of
these things reduce PoW's security by a factor of about 83% (1 - 50%*33%).

 > Proof of Stake requires other trade-offs which are incompatible with
Bitcoin's objective (to be a trustless digital cash) — specifically the
famous "security vs. liveness" guarantee

Do you have a good source that talks about why you think proof of stake
cannot be used for a trustless digital cash?

> You cannot gain tokens without someone choosing to give up those coins -
a form of permission.

This is not a practical constraint. Just like in mining, some nodes may
reject you, but there will likely be more that will accept you, some
sellers may reject you, but most would accept your money as payment for
bitcoins. I don't think requiring the "permission" of one of millions of
people in the market can be reasonably considered a "permissioned
currency".

> 2. Proof of stake must have a trusted means of timestamping to regulate
overproduction of blocks

Both PoW and PoS could mine/mint blocks twice as fast if everyone agreed to
double their clock speeds. Both systems rely on an honest majority sticking
to standard time.


On Wed, May 19, 2021 at 5:32 AM Michael Dubrovsky via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Ah sorry, I didn't realize this was, in fact, a different thread! :)
>
> On Wed, May 19, 2021 at 10:07 AM Michael Dubrovsky <mike@powx.org> wrote:
>
>> Folks, I suggest we keep the discussion to PoW, oPoW, and the BIP itself.
>> PoS, VDFs, and so on are interesting but I guess there are other threads
>> going on these topics already where they would be relevant.
>>
>> Also, it's important to distinguish between oPoW and these other
>> "alternatives" to Hashcash. oPoW is a true Proof of Work that doesn't alter
>> the core game theory or security assumptions of Hashcash and actually
>> contains SHA (can be SHA3, SHA256, etc hash is interchangeable).
>>
>> Cheers,
>> Mike
>>
>> On Tue, May 18, 2021 at 4:55 PM Erik Aronesty via bitcoin-dev <
>> bitcoin-dev@lists.linuxfoundation.org> wrote:
>>
>>> 1. i never suggested vdf's to replace pow.
>>>
>>> 2. my suggestion was specifically *in the context of* a working
>>> proof-of-burn protocol
>>>
>>> - vdfs used only for timing (not block height)
>>> - blind-burned coins of a specific age used to replace proof of work
>>> - the required "work" per block would simply be a competition to
>>> acquire rewards, and so miners would have to burn coins, well in
>>> advance, and hope that their burned coins got rewarded in some far
>>> future
>>> - the point of burned coins is to mimic, in every meaningful way, the
>>> value gained from proof of work... without some of the security
>>> drawbacks
>>> - the miner risks losing all of his burned coins (like all miners risk
>>> losing their work in each block)
>>> - new burns can't be used
>>> - old burns age out (like ASICs do)
>>> - other requirements on burns might be needed to properly mirror the
>>> properties of PoW and the incentives Bitcoin uses to mine honestly.
>>>
>>> 3. i do believe it is *possible* that a "burned coin + vdf system"
>>> might be more secure in the long run, and that if the entire space
>>> agreed that such an endeavor was worthwhile, a test net could be spun
>>> up, and a hard-fork could be initiated.
>>>
>>> 4. i would never suggest such a thing unless i believed it was
>>> possible that consensus was possible.  so no, this is not an "alt
>>> coin"
>>>
>>> On Tue, May 18, 2021 at 10:02 AM Zac Greenwood <zachgrw@gmail.com>
>>> wrote:
>>> >
>>> > Hi ZmnSCPxj,
>>> >
>>> > Please note that I am not suggesting VDFs as a means to save energy,
>>> but solely as a means to make the time between blocks more constant.
>>> >
>>> > Zac
>>> >
>>> >
>>> > On Tue, 18 May 2021 at 12:42, ZmnSCPxj <ZmnSCPxj@protonmail.com>
>>> wrote:
>>> >>
>>> >> Good morning Zac,
>>> >>
>>> >> > VDFs might enable more constant block times, for instance by having
>>> a two-step PoW:
>>> >> >
>>> >> > 1. Use a VDF that takes say 9 minutes to resolve (VDF being subject
>>> to difficulty adjustments similar to the as-is). As per the property of
>>> VDFs, miners are able show proof of work.
>>> >> >
>>> >> > 2. Use current PoW mechanism with lower difficulty so finding a
>>> block takes 1 minute on average, again subject to as-is difficulty
>>> adjustments.
>>> >> >
>>> >> > As a result, variation in block times will be greatly reduced.
>>> >>
>>> >> As I understand it, another weakness of VDFs is that they are not
>>> inherently progress-free (their sequential nature prevents that; they are
>>> inherently progress-requiring).
>>> >>
>>> >> Thus, a miner which focuses on improving the amount of energy that it
>>> can pump into the VDF circuitry (by overclocking and freezing the
>>> circuitry), could potentially get into a winner-takes-all situation,
>>> possibly leading to even *worse* competition and even *more* energy
>>> consumption.
>>> >> After all, if you can start mining 0.1s faster than the competition,
>>> that is a 0.1s advantage where *only you* can mine *in the entire world*.
>>> >>
>>> >> Regards,
>>> >> ZmnSCPxj
>>> _______________________________________________
>>> bitcoin-dev mailing list
>>> bitcoin-dev@lists.linuxfoundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>>
>>
>>
>> --
>> Michael Dubrovsky
>> Founder; PoWx
>> www.PoWx.org <http://www.powx.org/>
>>
>
>
> --
> Michael Dubrovsky
> Founder; PoWx
> www.PoWx.org <http://www.powx.org/>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

[-- Attachment #2: Type: text/html, Size: 13058 bytes --]