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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>,
 SatoshiSingh <SatoshiSingh@protonmail.com>,
 Billy Tetrud <billy.tetrud@gmail.com>
Subject: Re: [bitcoin-dev] Opinion on proof of stake in future
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Comments inline.



> > Could you explain what am I missing here, because this actually does no=
t seem better, but rather worse than some PoS schemes?
>
> Given your example, if !BTC is needed to burn, that's a $50k
> investment in an ASIC needed to mine a block. That's not anywhere
> near current levels. It's not even approaching the current PoW. A
> $50k investment to be a large amount of hash power is ... well,
> somewhere more than 10 years ago.

This is +- true with todays prices, that was not my point. We all know that=
 today's total block revenue is nowhere near 1 BTC. If it is say 7 BTC, the=
n we would expect that the miners spend roughly just about 7 BTC to produce=
 the block - in long term, on average. Right? Today, this 7 BTC is supposed=
 to be some average of investment into the mining rig, the building in whic=
h the rig exists (or its rent) and then some electricity. So when I said 1 =
BTC I meant that amount of BTC that is the sum of the block subsidy and fee=
s at the time of this imagined switch to PoB. Use 7 BTC if you want to talk=
 today. And yes, that seems very weak. But can you explain why it is not th=
e case after switching to PoB that the cost of producing the block should r=
oughly converge to to the revenue? Because I do not see why would miners sp=
end more than what they can earn.





> My original proof-of-burn concept was designed to mimic ASICs as much
> as possible:
>
> 1.  large initial investment (burn to acquire power)
> 2.  continued investment (burn to activate power in each block, lost if
>     block is not found)
>
>     Ideally, the attacker would have to keep burning for each lottery
>     ticket, which can only be used once. Committing that burn to a
>     particular block for example.
>
>     Any attack you propose for a "assumed well designed PoB" can also att=
ack PoW.
>     Any attack you propose for a "assumed well designed PoB" can also att=
ack PoS.
>
>     But there are some things PoB can do that PoS can't... which is reall=
y
>     my original point.

This is the problem that I wanted to avoid. You refer to some "my original =
PoB", but I am strictly talking about the concept described in wiki because=
 nothing else was provided to me. If we do not have a reference description=
 of what you are talking about the debate will quickly turn into the classi=
cal debate with PoS supporters - I explain an attack and they "patch it", c=
reating problem elsewhere. Then I explain an attack against that and they p=
atch it there. And this goes infinitely.

So if there is some other version, better one than the one described in wik=
i, please let me know. If there is not, there is nothing to talk about real=
ly. You'd first need to define your model properly and describe very detail=
s of how it should work and then we can analyze it. It does not make much s=
ense to me to analyze a ghost protocol that I always only see a tiny part o=
f.

For example here above in the quoted text you mention some continual lost (=
if block is not found). If that is not the exponential decay as described i=
n the wiki, then I have no idea what it is. I do not say that I can't imagi=
ne for myself what it could be, but it is up to you to define it, so we can=
 be sure we are talking about the same thing.

Same with those early unblinding of burns - nothing about that in the wiki,=
 so that concept is alien to me and it can not be subject to a debate befor=
e it is precisely described.




>
>
> -   sunk costs/lost investment
> -   "hashpower" is "offline", and cannot be seized.
>
>     On Tue, Jun 1, 2021 at 4:21 AM befreeandopen
>     befreeandopen@protonmail.com wrote:
>
>
> > Erik, thanks for the link. So referring to https://en.bitcoin.it/wiki/P=
roof_of_burn, I do not really understand how this is supposed to be that mu=
ch better over many proof of stake proposals. If there is more research on =
PoB, please note I'm not commenting on that as I only read this wiki articl=
e and my comments are purely related to this only.
> > I hope we can agree that the idea with manual insertion of entropy ever=
y week can be discarded, but at the same time I don't think it is a crucial=
 point of the whole idea. So we can just focus on the rest of it.
> > Then the whole idea seems just like certain proof of stake implementati=
ons with just small differences, which I try to summarize:
> >
> > -   in PoB, in order to use the coin for block production, you burn it =
in the past and wait some time -- in the certain PoS I'm talking about, in =
order to use the coin, you do not move the coin for some time - so in both =
there is the same idea - you somehow make the coin eligible for the block c=
reation process by first doing some action followed by some inaction for so=
me time; the difference here is that if later you use such coin in PoS, the=
n after waiting more time, you can use the coin again (for whatever purpose=
), while in PoB the coin is gone forever (it is burned); this does not seem=
 to be fundamentally different
> >
> > -   in PoB, the author suggests there is an exponential decay of the po=
wer of the coin to create a block; in some PoS schemas, there historically =
was an era of so called CoinAge mechanism, which was somewhat inverse to th=
is exponential decay, it was that the coin gets more power the older it is =
untouched, some implementations were for linear increase in the power, some=
 exponential. Usually there was a certain limit - i.e. a maximum power the =
coin may have reached. It turned out quite quickly that such property is ma=
king attacks easier. PoB reverses the idea, but I don't think that helps th=
at much. In any case, there seems to be an optimal period of time for each =
used coin, in both PoS and PoB, where the coin is most suitable for block p=
roduction. I admit PoB version is better, but the crucial property here is =
that some coins are more powerful than other.
> >
> > -   in both PoB and PoS it seems there is linear increase of the abilit=
y of the coin to produce blocks with the size of the coin (more BTC you bur=
n/stake, the better your chance)
> >
> >
> > This characteristic of PoB does not suggest that it would have that muc=
h different properties than PoS. So it should suffer from same problems as =
PoS. Namely, the problems I see now, with the given proposal from wiki, are=
:
> >
> > -   there seems to be lack of definition of the heaviest chain and diff=
iculty adjustment - this seems crucial, but likely solvable, I'm just sayin=
g it is importantly missing in the description
> >
> > -   there seems to be a problem with nothing at stake (nothing at burn =
maybe?) - How that can be? Again, it seems that every burned coin can be us=
ed for free checks at any time after the initial waiting period. These free=
 checks are indeed free and are the core of the nothing at stake problem in=
 PoS. You seem to make those checks for free and you seem to be able to use=
 those burned coins to create arbitrary number of forks build on any parent=
 blocks of your choice, not just the last block of the heaviest chain. I ca=
n't see at the moment how is this different from PoS nothing at stake probl=
em. Maybe you can explain?
> >
> > -   it seems to me that there is a trivial attack against the scheme by=
 a wealthy attacker. Suppose a common size of the burn is 1 BTC per block, =
suppose you define the heaviest chain rule somehow in relation to total num=
ber of burned coins or the cumulative "strength" of the "lowest" hashes, th=
en you can just burn 20 UTXOs, each being 10 BTC in value, so you spent 200=
 BTC on this attack, but you are in very strong position because after you =
wait the needed time, you should be able to do pretty nasty reorg. Suppose =
that the main chain is A-B-C-D-E-F, so what you do at that point is that yo=
u just "try for free" all your 20 UTXOs, whether or not they can build on t=
op of block A (which has 5 confs on top, F is the tip of the main chain). S=
ince you have big UTXOs, your chances should be good, of course you can alw=
ays try many times because you have a "lottery ticket" for every timestampt=
 t. So with this you should be able, with good chance, to find such B' and =
then you have 19 UTXOs remaining to try to build on B' in the same way. I c=
an't see what prevents this attack in the described scheme.
> >
> > -   the ability to retroactively try all different kids of timestamp t =
seems devastating - you again get super easy and somewhat cheap attack (due=
 to nothing at burn problem) that allows you to rewrite even long chains at=
 will.
> >
> >
> > Could you explain what am I missing here, because this actually does no=
t seem better, but rather worse than some PoS schemes?
> > Sent with ProtonMail Secure Email.
> > =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Origina=
l Message =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=
=90
> > On Friday, May 28, 2021 9:06 PM, Erik Aronesty erik@q32.com wrote:
> >
> > > best writeup i know of is here:
> > > https://en.bitcoin.it/wiki/Proof_of_burn
> > > no formal proposals or proofs that i know of.
> > > On Fri, May 28, 2021 at 10:40 AM befreeandopen
> > > befreeandopen@protonmail.com wrote:
> > >
> > > > Erik, I am sorry, I have little knowledge about proof-of-burn, I ne=
ver found it interesting up until now. Some of your recent claims seem quit=
e strong to me and I'd like to read more.
> > > > Forgive me if this has been mentioned recently, but is there a full=
 specification of the concept you are referring to? I don't mean just the b=
asic idea description (that much is clear to me), I mean a fully detailed p=
roposal or technical documentation that would give me a precise information=
 about what exactly it is that you are talking about.
> > > > Sent with ProtonMail Secure Email.
> > > > =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Ori=
ginal Message =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=
=E2=80=90
> > > > On Wednesday, May 26, 2021 11:07 PM, Erik Aronesty erik@q32.com wro=
te:
> > > >
> > > > > note: the "nothing at stake" problem you propose is not broken fo=
r
> > > > > proof-of-burn, because the attacker
> > > > > a) has no idea which past transactions are burns
> > > > > b) has no way to use his mining power, even 5%, to maliciously im=
prove
> > > > > his odds of being selected
> > > > > On Wed, May 26, 2021 at 9:12 AM befreeandopen
> > > > > befreeandopen@protonmail.com wrote:
> > > > >
> > > > > > @befreeandopen I guess I misunderstood your selfish minting att=
ack. Let me make sure I understand it. You're saying it would go as follows=
?:
> > > > > >
> > > > > > 1.  The malicious actor comes across an opportunity to mint the=
 next 3 blocks. But they hold off and don't release their blocks just yet.
> > > > > > 2.  They receive a new block minted by someone else.
> > > > > > 3.  The malicious actor then chooses to release their other 2 b=
locks on on the second from the top block if it gives them more blocks in t=
he future than minting on the top block. And instead lets the top block pro=
ceed if it gives them more blocks in the future (also figuring in the 3 blo=
cks they're missing out on minting).
> > > > > > 4.  Profit!
> > > > > >
> > > > > > The problem with this attack is that any self respecting PoS sy=
stem wouldn't have the information available for minters to know how blocks=
 will affect their future prospects of minting. Otherwise this would introd=
uce the problem of stake grinding. This can be done using collaborative ran=
domness (where numbers from many parties are combined to create a random nu=
mber that no individual party could predict). In fact, that's what the Casp=
er protocol does to decide quorums. In a non quorum case, you can do someth=
ing like record a hash of a number in the block header, and then have a sec=
ond step to release that number later. Rewards can be given can be used to =
ensure minters act honestly here by minting messages that release these num=
bers and not releasing their secret numbers too early.
> > > > > > Yes, you misunderstood it. First, let me say that the above tho=
ughts of yours are incorrect, at least for non-quorum case. Since the trans=
ition in the blockchain system from S1 to S2 is only by adding new block, a=
nd since stakers always need to be able to decide whether or not they can a=
dd the next block, it follows that if a staker creates a new block locally,=
 she can decide whether the new state allows her to add another block on to=
p. As you mentioned, this COULD introduce problem of staking, that you are =
incorrect in that it is a necessity. Usual prevention of the grinding probl=
em in this case is that an "old enough" source of randomness applies for th=
e current block production process. Of course this, as it is typical for Po=
S, introduces other problems, but let's discard those.
> > > > > > I will try to explain in detail what you misunderstood before. =
You start with a chain ending with blocks A-B-C, C being the top, the commo=
n feature of PoS system (non-quorum), roughly speaking, is that if N is the=
 total amount of coins that participate in the staking process to create a =
new block on top of C (let's call that D), then a participant having K*N am=
ount of stake has chance K to be the one who will create the next stake. In=
 other words, the power of stakers is supposed to be linear in the system -=
 you own 10 coins gives you 10x the chance of finding block over someone wh=
o has 1 coin.
> > > > > > What i was claiming is that using the technique I have describe=
d, this linearity is violated. Why? Well, it works for honest stakers among=
 the competition of honest stakers - they really do have the chance of K to=
 find the next block. However, the attacker, using nothing at stake, checks=
 her ability to build block D (at some timestamp). If she is successful, sh=
e does not propagate D immediately, but instead she also checks whether she=
 can build on top of B and on top of A. Since with every new timestamp, usu=
ally, there is a new chance to build the block, it is not uncommon that she=
 finds she is indeed able to build such block C' on top of B. Here it is li=
kely t(C') > t(C) as the attacker has relatively low stake. Note that in or=
der to produce such C', she not only could have tried the current timestamp=
 t(D), but also all previous timestamps up to t(B) (usually that's the cons=
ensus rule, but it may depend on a specific consensus). So her chance to pr=
oduce such C' is greater than her previous chance of producing C (which cha=
nce was limited by other stakers in the system and the discovery of block C=
 by one of them). Now suppose that she found such C' and now she continues =
by trying to prolong this chain by finding D'. And again here, it is quite =
likely that her chance to find such D' is greater than was her chance of fi=
nding D because again there are likely multiple timestamps she could try. T=
his all was possible just because nothing at stake allows you to just try i=
f you can produce a block in certain state of block chain or not. Now if sh=
e actually was able to find D', she discards D and only publishes chain A-B=
-C'-D', which can not be punished despite the fact that she indeed produced=
 two different forks. She can not be punished because this production was l=
ocal and only the final result of A-B-C'-D' was published, in which case sh=
e gained an extra block over the honest strategy which would only give her =
block D.
> > > > > > Fun fact tho: there is an attack called the "selfish mining att=
ack" for proof of work, and it reduces the security of PoW by at least 1/3r=
d.
> > > > > > How is that relevant to our discussion? This is known research =
that has nothing to do with PoS except that it is often worse on PoS.
> > > > > >
> > > > > > > the problem is not as hard as you think
> > > > > >
> > > > > > I don't claim to know just how hard finding the IP address asso=
ciated with a bitcoin address is. However, the DOS risk can be solved more =
completely by only allowing the owner of coins themselves to know whether t=
hey can mint a block. Eg by determining whether someone can mint a block ba=
sed on their public key hidden behind hashes (as normal in addresses). Only=
 when someone does in fact mint a block do they reveal their hidden public =
key in order to prove they are allowed to mint the block.
> > > > > > This is true, but you are mixing quorum and non-quorum systems.=
 My objection here was towards such system where I specifically said that t=
he list of producers for next epoch is known up front and you confirmed tha=
t this is what you meant with "quorum" system. So in such system, I claimed=
, the known producer is the only target at any given point of time. This of=
 course does not apply to any other type of system where future producers a=
re not known. No need to dispute, again, something that was not claimed.
> > > > > >
> > > > > > > I agree that introduction of punishment itself does not imply=
 introducing a problem elsewhere (which I did not claim if you reread my pr=
evious message)
> > > > > >
> > > > > > I'm glad we agree there. Perhaps I misunderstood what you meant=
 by "you should not omit to mention that by doing so, typically, you have i=
ntroduced another problem elsewhere."
> > > > > > Perhaps you should quote the full sentence and not just a part =
of it:
> > > > > > "Of course you can always change the rules in a way that a cert=
ain specific attack is not doable, but you should not omit to mention that =
by doing so, typically, you have introduced another problem elsewhere, or y=
ou have not solved it completely."
> > > > > > You can parse this as: (CREATE PROBLEM ELSEWHERE) OR (NOT SOLVE=
 IT COMPLETELY)
> > > > > > In case of the punishment it was meant to be the not solve it c=
ompletely part.
> > > > > > Also "typically" does not imply always.
> > > > > > But this parsing of English sentences for you seems very off to=
pic here. My point is, in context of Bitcoin, reject such unsupported claim=
s that PoS is a reasonable alternative to PoW, let's stick to that.
> > > > > >
> > > > > > > As long as the staker makes sure (which is not that hard) tha=
t she does not miss a chance to create a block, her significance in the sys=
tem will always increase in time. It will increase relative to all normal u=
sers who do not stake
> > > > > >
> > > > > > Well, if you're in the closed system of the cryptocurrency, sur=
e. But we don't live in that closed system. Minters will earn some ROI from=
 minting just like any other financial activity. Others may find more succe=
ss spending their time doing things other than figuring out how to mint coi=
ns. In that case, they'll be able to earn more coin that they could later d=
ecide to use to mint blocks if they decide to.
> > > > > > This only supports the point I was making. Since the optimal sc=
enario with all existing coins participating is just theoretical, the attac=
ker's position will ever so improve. It seems we are in agreement here, gre=
at.
> > > > > >
> > > > > > > Just because of the above we must reject PoS as being critica=
lly insecure
> > > > > >
> > > > > > I think the only thing we can conclude from this is that you ha=
ve come up with an insecure proof of stake protocol. I don't see how anythi=
ng you've brought up amounts to substantial evidence that all possible PoS =
protocols are insecure.
> > > > > > I have not come up with anything. I'm afraid you've not realize=
d the burden of proof is on your side if you vouch for a design that is not=
 believed and trusted to be secure. It is up to you to show that you know h=
ow to solve every problem that people throw at you. So far we have just dem=
onstrated that your claim that nothing at stake is solved was unjustified. =
You have not described a system that would solve it (and not introduce crit=
ical DDOS attack vector as it is in quorum based systems - per the prior de=
finition of such systems).
> > > > > > Of course the list of problems of PoS systems do not end with j=
ust nothing at stake, but it is good enough example that by itself prevents=
 its adoption in decentralized consensus. No need to go to other hard probl=
ems without solving nothing at stake.
> > > > > > On Tue, May 25, 2021 at 11:10 AM befreeandopen befreeandopen@pr=
otonmail.com wrote:
> > > > > >
> > > > > > > @befreeandopen " An attacker can calculate whether or not she=
 can prolong this chain or not and if so with what timestamp."
> > > > > > > The scenario you describe would only be likely to happen at a=
ll if the malicious actor has a very large fraction of the stake - probably=
 quite close to 50%. At that point, you're talking about a 51% attack, not =
the nothing at stake problem. The nothing at stake problem is the problem w=
here anyone will mint on any chain. Its clear that if there's a substantial=
 punishment for minting on chains other than the one that eventually wins, =
every minter without a significant fraction of the stake will be honest and=
 not attempt to mint on old blocks or support someone else's attempt to min=
t on old blocks (until and if it becomes the heaviest chain). Because the a=
ttacker would need probably >45% of the active stake (take a look at the re=
asoning here for a deeper analysis of that statement), I don't agree that p=
unishment is not a sufficient mitigation of the nothing at stake problem. T=
o exploit the nothing at stake problem, you basically need to 51% attack, a=
t which point you've exceeded the operating conditions of the system, so of=
 course its gonna have problems, just like a 51% attack would cause with Po=
W.
> > > > > > > This is not at all the case. The attacker benefits using the =
described technique at any size of the stake and significantly so with just=
 5% of the stake. By significantly, I do not mean that the attacker is able=
 to completely take control the network (in short term), but rather that th=
e attacker has significant advantage in the number of blocks she creates co=
mpared to what she "should be able to create". This means the attacker's st=
ake increases significantly faster than of the honest nodes, which in long =
term is very serious in PoS system. If you believe close to 50% is needed f=
or that, you need to redo your math. So no, you are wrong stating that "to =
exploit nothing at stake problem you basically need to 51% attack". It is r=
ather the opposite - eventually, nothing at stake attack leads to ability t=
o perform 51% attack.
> > > > > > >
> > > > > > > > I am not sure if this is what you call quorum-based PoS
> > > > > > >
> > > > > > > Yes, pre-selected minters is exactly what I mean by that.
> > > > > > >
> > > > > > > > it allows the attacker to know who to attack at which point=
 with powerful DDOS in order to hurt liveness of such system
> > > > > > >
> > > > > > > Just like in bitcoin, associating keys with IP addresses isn'=
t generally an easy thing to do on the fly like that. If you know someone's=
 IP address, you can target them. But if you only know their address or pub=
lic key, the reverse isn't as easy. With a quorum-based PoS system, you can=
 see their public key and address, but finding out their IP to DOS would be=
 a huge challenge I think.
> > > > > > > I do not dispute that the problem is not trivial, but the pro=
blem is not as hard as you think. The network graph analysis is a known tec=
hnique and it is not trivial, but not very hard either. Introducing a large=
 number of nodes to the system to achieve very good success rate of analysi=
s of area of origin of blocks is doable and has been done in past. So again=
, I very much disagree with your conclusion that this is somehow secure. It=
 is absolutely insecure.
> > > > > > > Note, tho, that quorum-based PoS generally also have punishme=
nts as part of the protocol. The introduction of punishments do indeed hand=
ily solve the nothing at stake problem. And you didn't mention a single pro=
blem that the punishments introduce that weren't already there before punis=
hments. There are tradeoffs with introducing punishments (eg in some cases =
you might punish honest actors), but they are minor in comparison to solvin=
g the nothing at stake problem.
> > > > > > > While I agree that introduction of punishment itself does not=
 imply introducing a problem elsewhere (which I did not claim if you reread=
 my previous message), it does introduce additional complexity which may in=
troduce problem, but more importantly, while it slightly improves resistanc=
e against the nothing at stake attack, it solves absolutely nothing. Your c=
laim is based on wrong claim of needed close to 50% stake, but that could n=
ot be farther from the truth. It is not true even in optimal conditions whe=
n all participants of the network stake or delegate their stake. These opti=
mal conditions rarely, if ever, occur. And that's another thing that we hav=
e not mention in our debate, so please allow me to introduce another proble=
m to PoS.
> > > > > > > Consider what is needed for such optimal conditions to occur =
- all coins are always part of the stake, which means that they need to som=
ehow automatically part of the staking process even when they are moved. Bu=
t in many PoS systems you usually require some age (in terms of confirmatio=
ns) of the coin before you allow it to be used for participation in staking=
 process and that is for a good reason - to prevent various grinding attack=
s. In some systems the coin must be specifically registered before it can b=
e staked, in others, simply waiting for enough confirmations enables you to=
 stake with the coin. I am not sure if there is a system which does not hav=
e this cooling period for a coin that has been moved. Maybe it is possible =
though, but AFAIK it is not common and not battle tested feature.
> > > > > > > Then if we admit that achieving the optimal condition is rath=
er theoretical. Then if we do not have the optimal condition, it means that=
 a staker with K% of the total available supply increases it's percentage o=
ver time to some amounts >K%. As long as the staker makes sure (which is no=
t that hard) that she does not miss a chance to create a block, her signifi=
cance in the system will always increase in time. It will increase relative=
 to all normal users who do not stake (if there are any) and relative to al=
l other stakers who make mistakes or who are not wealthy enough to afford n=
ot selling any position ever. But powerful attacker is exactly in such posi=
tion and thus she will gain significance in such a system. The technique I =
have described, and that you mistakenly think is viable only with huge amou=
nts of stake, only puts the attacker to even greater advantage. But even wi=
thout the described attack (which exploits nothing at stake), the PoS syste=
m converges to a system more and more controlled by powerful entity, which =
we can assume is the attacker.
> > > > > > > So I don't think it is at all misleading to claim that "nothi=
ng at stake" is a solved problem. I do in fact mean that the solutions to t=
hat problem don't introduce any other problems with anywhere near the same =
level of significance.
> > > > > > > It still stands as truly misleading claim. I disagree that in=
troducing DDOS opportunity with medium level of difficulty for the attacker=
 to implement it, in case of "quorum-based PoS" is not a problem anywhere n=
ear the same level of significance. Such an attack vector allows you to tur=
n off the network if you spend some time and money. That is hardly acceptab=
le.
> > > > > > > Just because of the above we must reject PoS as being critica=
lly insecure until someone invents and demonstrates an actual way of solvin=
g these issues.
> > > > > > > On Tue, May 25, 2021 at 3:00 AM Erik Aronesty erik@q32.com wr=
ote:
> > > > > > >
> > > > > > > > > > you burn them to be used at a future particular block h=
eight
> > > > > > > >
> > > > > > > > > This sounds exploitable. It seems like an attacker could =
simply focus all their burns on a particular set of 6 blocks to double spen=
d, minimizing their cost of attack.
> > > > > > > >
> > > > > > > > could be right. the original idea was to have burns decay o=
ver time,
> > > > > > > > like ASIC's.
> > > > > > > > anyway the point was not that "i had a magic formula"
> > > > > > > > the point was that proof of burn is almost always better th=
an proof of
> > > > > > > > stake - simply because the "proof" is on-chain, not sitting=
 on a node
> > > > > > > > somewhere waiting to be stolen.
> > > > > > > > On Mon, May 24, 2021 at 9:53 PM Billy Tetrud billy.tetrud@g=
mail.com wrote:
> > > > > > > >
> > > > > > > > > Is this the kind of proof of burn you're talking about?
> > > > > > > > >
> > > > > > > > > > if i have a choice between two chains, one longer and o=
ne shorter, i can only choose one... deterministically
> > > > > > > > >
> > > > > > > > > What prevents you from attempting to mine block 553 on bo=
th chains?
> > > > > > > > >
> > > > > > > > > > miners have a very strong, long-term, investment in the=
 stability of the chain.
> > > > > > > > >
> > > > > > > > > Yes, but the same can be said of any coin, even ones that=
 do have the nothing at stake problem. This isn't sufficient tho because th=
e chain is a common good, and the tragedy of the commons holds for it.
> > > > > > > > >
> > > > > > > > > > you burn them to be used at a future particular block h=
eight
> > > > > > > > >
> > > > > > > > > This sounds exploitable. It seems like an attacker could =
simply focus all their burns on a particular set of 6 blocks to double spen=
d, minimizing their cost of attack.
> > > > > > > > >
> > > > > > > > > > i can imagine scenarios where large stakeholders can co=
llude to punish smaller stakeholders simply to drive them out of business, =
for example
> > > > > > > > >
> > > > > > > > > Are you talking about a 51% attack? This is possible in a=
ny decentralized cryptocurrency.
> > > > > > > > > On Mon, May 24, 2021 at 11:49 AM Erik Aronesty erik@q32.c=
om wrote:
> > > > > > > > >
> > > > > > > > > > > > your burn investment is always "at stake", any reda=
ction can result in a loss-of-burn, because burns can be tied, precisely, t=
o block-heights
> > > > > > > > > > > > I'm fuzzy on how proof of burn works.
> > > > > > > > > >
> > > > > > > > > > when you burn coins, you burn them to be used at a futu=
re particular
> > > > > > > > > > block height: so if i'm burning for block 553, i can on=
ly use them to
> > > > > > > > > > mine block 553. if i have a choice between two chains, =
one longer
> > > > > > > > > > and one shorter, i can only choose one... deterministic=
ally, for that
> > > > > > > > > > burn: the chain with the height 553. if we fix the "lea=
d time" for
> > > > > > > > > > burned coins to be weeks or even months in advance, min=
ers have a very
> > > > > > > > > > strong, long-term, investment in the stability of the c=
hain.
> > > > > > > > > > therefore there is no "nothing at stake" problem. it's
> > > > > > > > > > deterministic, so miners have no choice. they can only =
choose the
> > > > > > > > > > transactions that go into the block. they cannot choose=
 which chain
> > > > > > > > > > to mine, and it's time-locked, so rollbacks and instabi=
lity always
> > > > > > > > > > hurt miners the most.
> > > > > > > > > > the "punishment" systems of PoS are "weird at best", ce=
rtainly
> > > > > > > > > > unproven. i can imagine scenarios where large stakehold=
ers can
> > > > > > > > > > collude to punish smaller stakeholders simply to drive =
them out of
> > > > > > > > > > business, for example. and then you have to put checks =
in place to
> > > > > > > > > > prevent that, and more checks for those prevention syst=
em...
> > > > > > > > > > in PoB, there is no complexity. simpler systems like th=
is are
> > > > > > > > > > typically more secure.
> > > > > > > > > > PoB also solves problems caused by "energy dependence",=
 which could
> > > > > > > > > > lead to state monopolies on mining (like the new Bitcoi=
n Mining
> > > > > > > > > > Council). these consortiums, if state sanctioned, could=
 become a
> > > > > > > > > > source of censorship, for example. Since PoB doesn't re=
quire you to
> > > > > > > > > > have a live, well-connected node, it's harder to censor=
 & harder to
> > > > > > > > > > trace.
> > > > > > > > > > Eliminating this weakness seems to be in the best inter=
ests of
> > > > > > > > > > existing stakeholders
> > > > > > > > > > On Mon, May 24, 2021 at 4:44 PM Billy Tetrud billy.tetr=
ud@gmail.com wrote:
> > > > > > > > > >
> > > > > > > > > > > > proof of burn clearly solves this, since nothing is=
 held online
> > > > > > > > > > >
> > > > > > > > > > > Well.. the coins to be burned need to be online when =
they're burned. But yes, only a small fraction of the total coins need to b=
e online.
> > > > > > > > > > >
> > > > > > > > > > > > your burn investment is always "at stake", any reda=
ction can result in a loss-of-burn, because burns can be tied, precisely, t=
o block-heights
> > > > > > > > > > >
> > > > > > > > > > > So you're saying that if say someone tries to mine a =
block on a shorter chain, that requires them to send a transaction burning =
their coins, and that transaction could also be spent on the longest chain,=
 which means their coins are burned even if the chain they tried to mine on=
 doesn't win? I'm fuzzy on how proof of burn works.
> > > > > > > > > > >
> > > > > > > > > > > > proof of burn can be more secure than proof-of-stak=
e
> > > > > > > > > > >
> > > > > > > > > > > FYI, proof of stake can be done without the "nothing =
at stake" problem. You can simply punish people who mint on shorter chains =
(by rewarding people who publish proofs of this happening on the main chain=
). In quorum-based PoS, you can punish people in the quorum that propose or=
 sign multiple blocks for the same height. The "nothing at stake" problem i=
s a solved problem at this point for PoS.
> > > > > > > > > > > On Mon, May 24, 2021 at 3:47 AM Erik Aronesty erik@q3=
2.com wrote:
> > > > > > > > > > >
> > > > > > > > > > > > > I don't see a way to get around the conflicting r=
equirement that the keys for large amounts of coins should be kept offline =
but those are exactly the coins we need online to make the scheme secure.
> > > > > > > > > > > >
> > > > > > > > > > > > proof of burn clearly solves this, since nothing is=
 held online
> > > > > > > > > > > >
> > > > > > > > > > > > > how does proof of burn solve the "nothing at stak=
e" problem in your view?
> > > > > > > > > > > >
> > > > > > > > > > > > definition of nothing at stake: in the event of a f=
ork, whether the
> > > > > > > > > > > > fork is accidental or a malicious, the optimal stra=
tegy for any miner
> > > > > > > > > > > > is to mine on every chain, so that the miner gets t=
heir reward no
> > > > > > > > > > > > matter which fork wins. indeed in proof-of-stake, t=
he proofs are
> > > > > > > > > > > > published on the very chains mines, so the incentiv=
e is magnified.
> > > > > > > > > > > > in proof-of-burn, your burn investment is always "a=
t stake", any
> > > > > > > > > > > > redaction can result in a loss-of-burn, because bur=
ns can be tied,
> > > > > > > > > > > > precisely, to block-heights
> > > > > > > > > > > > as a result, miners no longer have an incentive to =
mine all chains
> > > > > > > > > > > > in this way proof of burn can be more secure than p=
roof-of-stake, and
> > > > > > > > > > > > even more secure than proof of work
> > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > On Sun, May 23, 2021 at 3:52 AM Lloyd Fournier via =
bitcoin-dev
> > > > > > > > > > > > bitcoin-dev@lists.linuxfoundation.org wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > > Hi Billy,
> > > > > > > > > > > > > I was going to write a post which started by dism=
issing many of the weak arguments that are made against PoS made in this th=
read and elsewhere.
> > > > > > > > > > > > > Although I don't agree with all your points you h=
ave done a decent job here so I'll focus on the second part: why I think Pr=
oof-of-Stake is inappropriate for a Bitcoin-like system.
> > > > > > > > > > > > > Proof of stake is not fit for purpose for a globa=
l settlement layer in a pure digital asset (i.e. "digital gold") which is w=
hat Bitcoin is trying to be.
> > > > > > > > > > > > > PoS necessarily gives responsibilities to the hol=
ders of coins that they do not want and cannot handle.
> > > > > > > > > > > > > In Bitcoin, large unsophisticated coin holders ca=
n put their coins in cold storage without a second thought given to the hea=
lth of the underlying ledger.
> > > > > > > > > > > > > As much as hardcore Bitcoiners try to convince th=
em to run their own node, most don't, and that's perfectly acceptable.
> > > > > > > > > > > > > At no point do their personal decisions affect th=
e underlying consensus -- it only affects their personal security assurance=
 (not that of the system itself).
> > > > > > > > > > > > > In PoS systems this clean separation of responsib=
ilities does not exist.
> > > > > > > > > > > > > I think that the more rigorously studied PoS prot=
ocols will work fine within the security claims made in their papers.
> > > > > > > > > > > > > People who believe that these protocols are desti=
ned for catastrophic consensus failure are certainly in for a surprise.
> > > > > > > > > > > > > But the devil is in the detail.
> > > > > > > > > > > > > Let's look at what the implications of using the =
leading proof of stake protocols would have on Bitcoin:
> > > > > > > > > > > > >
> > > > > > > > > > > > > ### Proof of SquareSpace (Cardano, Polkdadot)
> > > > > > > > > > > > >
> > > > > > > > > > > > > Cardano is a UTXO based PoS coin based on Ourobor=
os Praos3 with an inbuilt on-chain delegation system5.
> > > > > > > > > > > > > In these protocols, coin holders who do not want =
to run their node with their hot keys in it delegate it to a "Stake Pool".
> > > > > > > > > > > > > I call the resulting system Proof-of-SquareSpace =
since most will choose a pool by looking around for one with a nice website=
 and offering the largest share of the block reward.
> > > > > > > > > > > > > On the surface this might sound no different than=
 someone with an mining rig shopping around for a good mining pool but ther=
e are crucial differences:
> > > > > > > > > > > > >
> > > > > > > > > > > > > 1.  The person making the decision is forced into=
 it just because they own the currency -- someone with a mining rig has pur=
chased it with the intent to make profit by participating in consensus.
> > > > > > > > > > > > >
> > > > > > > > > > > > > 2.  When you join a mining pool your systems are =
very much still online. You are just partaking in a pool to reduce your pro=
fit variance. You still see every block that you help create and you never =
help create a block without seeing it first.
> > > > > > > > > > > > >
> > > > > > > > > > > > > 3.  If by SquareSpace sybil attack you gain a dis=
honest majority and start censoring transactions how are the users meant to=
 redelegate their stake to honest pools?
> > > > > > > > > > > > >     I guess they can just send a transaction dele=
gating to another pool...oh wait I guess that might be censored too! This s=
eems really really bad.
> > > > > > > > > > > > >     In Bitcoin, miners can just join a different =
pool at a whim. There is nothing the attacker can do to stop them. A tempor=
ary dishonest majority heals relatively well.
> > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > There is another severe disadvantage to this on-c=
hain delegation system: every UTXO must indicate which staking account this=
 UTXO belongs to so the appropriate share of block rewards can be transferr=
ed there.
> > > > > > > > > > > > > Being able to associate every UTXO to an account =
ruins one of the main privacy advantages of the UTXO model.
> > > > > > > > > > > > > It also grows the size of the blockchain signific=
antly.
> > > > > > > > > > > > >
> > > > > > > > > > > > > ### "Pure" proof of stake (Algorand)
> > > > > > > > > > > > >
> > > > > > > > > > > > > Algorand's4 approach is to only allow online stak=
e to participate in the protocol.
> > > > > > > > > > > > > Theoretically, This means that keys holding funds=
 have to be online in order for them to author blocks when they are chosen.
> > > > > > > > > > > > > Of course in reality no one wants to keep their c=
oin holding keys online so in Alogorand you can authorize a set of "partici=
pation keys"1 that will be used to create blocks on your coin holding key's=
 behalf.
> > > > > > > > > > > > > Hopefully you've spotted the problem.
> > > > > > > > > > > > > You can send your participation keys to any malic=
ious party with a nice website (see random example 2) offering you a good r=
eturn.
> > > > > > > > > > > > > Damn it's still Proof-of-SquareSpace!
> > > > > > > > > > > > > The minor advantage is that at least the particip=
ation keys expire after a certain amount of time so eventually the SquareSp=
ace attacker will lose their hold on consensus.
> > > > > > > > > > > > > Importantly there is also less junk on the blockc=
hain because the participation keys are delegated off-chain and so are not =
making as much of a mess.
> > > > > > > > > > > > >
> > > > > > > > > > > > > ### Conclusion
> > > > > > > > > > > > >
> > > > > > > > > > > > > I don't see a way to get around the conflicting r=
equirement that the keys for large amounts of coins should be kept offline =
but those are exactly the coins we need online to make the scheme secure.
> > > > > > > > > > > > > If we allow delegation then we open up a new soci=
al attack surface and it degenerates to Proof-of-SquareSpace.
> > > > > > > > > > > > > For a "digital gold" like system like Bitcoin we =
optimize for simplicity and desperately want to avoid extraneous responsibi=
lities for the holder of the coin.
> > > > > > > > > > > > > After all, gold is an inert element on the period=
ic table that doesn't confer responsibilities on the holder to maintain the=
 quality of all the other bars of gold out there.
> > > > > > > > > > > > > Bitcoin feels like this too and in many ways is m=
ore inert and beautifully boring than gold.
> > > > > > > > > > > > > For Bitcoin to succeed I think we need to keep it=
 that way and Proof-of-Stake makes everything a bit too exciting.
> > > > > > > > > > > > > I suppose in the end the market will decide what =
is real digital gold and whether these bad technical trade offs are worth b=
eing able to say it uses less electricity. It goes without saying that maki=
ng bad technical decisions to appease the current political climate is an a=
nathema to Bitcoin.
> > > > > > > > > > > > > Would be interested to know if you or others thin=
k differently on these points.
> > > > > > > > > > > > > Cheers,
> > > > > > > > > > > > > LL
> > > > > > > > > > > > > On Fri, 21 May 2021 at 19:21, Billy Tetrud via bi=
tcoin-dev bitcoin-dev@lists.linuxfoundation.org wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > > I think there is a lot of misinformation and bi=
as against Proof of Stake. Yes there have been lots of shady coins that use=
 insecure PoS mechanisms. Yes there have been massive issues with distribut=
ion of PoS coins (of course there have also been massive issues with PoW co=
ins as well). However, I want to remind everyone that there is a difference=
 between "proved to be impossible" and "have not achieved recognized succes=
s 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 Po=
S system. I certainly don't think we should experiment with bitcoin by swit=
ching to PoS, but from my research, it seems very likely that there is a pr=
oof of stake consensus protocol we could build that has substantially highe=
r 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 reli=
es on. I think the critical piece of this is the disagreements around hardc=
oded checkpoints, which is a critical piece solving attacks that could be l=
evied on a PoS chain, and how that does (or doesn't) affect the security mo=
del.
> > > > > > > > > > > > > > @Eric Your proof of stake fallacy seems to be s=
aying that PoS is worse when a 51% attack happens. While I agree, I think t=
hat line of thinking omits important facts:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > -   The capital required to 51% attack a PoS ch=
ain 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 unacceptab=
le. It should be considered whether what happens in the case of a 51% may n=
ot be significantly different. The currency would likely be critically dama=
ged in a 51% attack regardless of consensus mechanism.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Proof-of-stake tends towards oligopolistic co=
ntrol
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > 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 min=
t 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 doe=
s. Both of these mean the tendency towards oligopolistic control is worse f=
or PoW.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Energy usage, in-and-of-itself, is nothing to=
 be ashamed of!!
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I certainly agree. Bitcoin's energy usage at th=
e moment is I think quite warranted. However, the question is: can we do su=
bstantially better. I think if we can, we probably should... eventually.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Proof of Stake is only resilient to =E2=85=
=93 of the network demonstrating a Byzantine Fault, whilst Proof of Work is=
 resilient up to the =C2=BD threshold
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I see no mention of this in the pos.pdf you lin=
ked to. I'm not aware of any proof that all PoS systems have a failure thre=
shold 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 t=
o 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 attac=
ker does not need to obtain 100 exahashes/s, but actually only needs to acc=
umulate 50 exahashes/s. This is because as the attacker accumulates hashpow=
er, it drives honest miners out of the market as the difficulty increases t=
o beyond what is economically sustainable. Also, its been shown that the be=
st proof of work can do is require an attacker to obtain 33% of the hashpow=
er because of the selfish mining attack discussed in depth in this paper: h=
ttps://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 whic=
h are incompatible with Bitcoin's objective (to be a trustless digital cash=
) =E2=80=94 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 choosi=
ng to give up those coins - a form of permission.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > This is not a practical constraint. Just like i=
n mining, some nodes may reject you, but there will likely be more that wil=
l 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 o=
f millions of people in the market can be reasonably considered a "permissi=
oned 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 a=
s fast if everyone agreed to double their clock speeds. Both systems rely o=
n an honest majority sticking to standard time.
> > > > > > > > > > > > > > On Wed, May 19, 2021 at 5:32 AM Michael Dubrovs=
ky 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 Dubr=
ovsky 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 g=
uess 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 W=
ork that doesn't alter the core game theory or security assumptions of Hash=
cash and actually contains SHA (can be SHA3, SHA256, etc hash is interchang=
eable).
> > > > > > > > > > > > > > > > Cheers,
> > > > > > > > > > > > > > > > Mike
> > > > > > > > > > > > > > > > On Tue, May 18, 2021 at 4:55 PM Erik Arones=
ty via bitcoin-dev bitcoin-dev@lists.linuxfoundation.org wrote:
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > 1.  i never suggested vdf's to replace po=
w.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > 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 s=
imply be a competition to
> > > > > > > > > > > > > > > > >     acquire rewards, and so miners would =
have to burn coins, well in
> > > > > > > > > > > > > > > > >     advance, and hope that their burned c=
oins 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... wi=
thout some of the security
> > > > > > > > > > > > > > > > >     drawbacks
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > -   the miner risks losing all of his bur=
ned 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 "b=
urned coin + vdf system"
> > > > > > > > > > > > > > > > >     might be more secure in the long run,=
 and that if the entire space
> > > > > > > > > > > > > > > > >     agreed that such an endeavor was wort=
hwhile, a test net could be spun
> > > > > > > > > > > > > > > > >     up, and a hard-fork could be initiate=
d.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > 4.  i would never suggest such a thing un=
less 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 Gree=
nwood zachgrw@gmail.com wrote:
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > Hi ZmnSCPxj,
> > > > > > > > > > > > > > > > > > Please note that I am not suggesting VD=
Fs as a means to save energy, but solely as a means to make the time betwee=
n 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 blo=
ck times, for instance by having a two-step PoW:
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > 1.  Use a VDF that takes say 9 minu=
tes 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 subjec=
t to as-is difficulty adjustments.
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > As a result, variation in block tim=
es will be greatly reduced.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > As I understand it, another weakness =
of VDFs is that they are not inherently progress-free (their sequential nat=
ure prevents that; they are inherently progress-requiring).
> > > > > > > > > > > > > > > > > > > Thus, a miner which focuses on improv=
ing the amount of energy that it can pump into the VDF circuitry (by overcl=
ocking and freezing the circuitry), could potentially get into a winner-tak=
es-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
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > --
> > > > > > > > > > > > > > > Michael Dubrovsky
> > > > > > > > > > > > > > > Founder; PoWx
> > > > > > > > > > > > > > > www.PoWx.org
> > > > > > > > > > > > > > > bitcoin-dev mailing list
> > > > > > > > > > > > > > > bitcoin-dev@lists.linuxfoundation.org
> > > > > > > > > > > > > > > https://lists.linuxfoundation.org/mailman/lis=
tinfo/bitcoin-dev
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > bitcoin-dev mailing list
> > > > > > > > > > > > > > bitcoin-dev@lists.linuxfoundation.org
> > > > > > > > > > > > > > https://lists.linuxfoundation.org/mailman/listi=
nfo/bitcoin-dev
> > > > > > > > > > > > >
> > > > > > > > > > > > > bitcoin-dev mailing list
> > > > > > > > > > > > > bitcoin-dev@lists.linuxfoundation.org
> > > > > > > > > > > > > https://lists.linuxfoundation.org/mailman/listinf=
o/bitcoin-dev