Return-Path: Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 516BFC0001 for ; Tue, 25 May 2021 20:02:16 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 2215783403 for ; Tue, 25 May 2021 20:02:16 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -2.098 X-Spam-Level: X-Spam-Status: No, score=-2.098 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Authentication-Results: smtp1.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id YBWpzee19ANr for ; Tue, 25 May 2021 20:02:12 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.8.0 Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by smtp1.osuosl.org (Postfix) with ESMTPS id 1FCA583133 for ; Tue, 25 May 2021 20:02:11 +0000 (UTC) Received: by mail-ed1-x52e.google.com with SMTP id t15so37730296edr.11 for ; Tue, 25 May 2021 13:02:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GC22tCK7i91/H/+rGPG4uIU7qCQXXE61iXpNhHaJyVo=; b=R0R0OoJDuUS9AQN51y2OGMaL8lwKlEQG5AWV10uKDWr/ONVu9YwSTjbywWbGIZ6sCw O07U+ydv1VMD7bVhTepD8QGcl0RvpEQ55Mfyi2eSZWJgXL45qfnZY0CKEFB3j1Ub8pM/ U7tDBcgAJYPdhyjrFTbQdWYa1KjRVdg727c2lAerrSZK/GOgr0e6BA8L6oYPxp2x4lhV 93+5rY9J/XasSeXL7Nn7LGuuQ1ZGcEaRHs1KucXgV4KKBLUfF6OlnWoZPbQ7nsYb6Kx7 BLt7xqh2Yc9vSZzXS+poRTFOl2QhS66yffcblrATimgFg/T459JYmjfMFW2oCclmdEYw MKFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GC22tCK7i91/H/+rGPG4uIU7qCQXXE61iXpNhHaJyVo=; b=DwmscBWADlK7KYqcumHypt6ECA92gnU+6E++Ni0982V2MCNFDv1FvZK6YGqLFrxitS E07C2ciDW4hrlsZ0D/TXXVHba50kZScBbPCM8oBuK+GcQikvtVIw9sU8pOtfCQ/Hx91k OyhU1IDuG/d2NNhuYIIhkMawBNzYDZlM1ERbDStLUtz+vviWXvus9BkXwoZ0oxTmdFBc Fs1fnymYStKi4iK9nkDCPV+FK+/SJE+ps6i1vokwhZ7pY/u5hQttxjy1Y8YJK/gc+jVD aTH1rNx6MQl72lAhtzgtoR8JtfEx5idNZMt4u7HWESlgGtzP2jLgADqwX5yPSAheufYU u7xQ== X-Gm-Message-State: AOAM530YRZGNrQDz8pHmBOABbgjvls0pfkeNZYv8/zK/wwLlyFTII9sm TieCTP/zCm2nRmPDoSijBfYNb+b+1ZVmP9j7RUA= X-Google-Smtp-Source: ABdhPJxxMsKk6phBSCYp68dC8j5BTXaCB3vq/kWis8U/5s7ixzi/RfWl4Ug6pEXb0gLSeSm/tCiLQtQX2dr07kBni4Y= X-Received: by 2002:a05:6402:510b:: with SMTP id m11mr10827841edd.26.1621972930186; Tue, 25 May 2021 13:02:10 -0700 (PDT) MIME-Version: 1.0 References: <6do5xN2g5LPnFeM55iJ-4C4MyXOu_KeXxy68Xt4dJQMhi3LJ8ZrLICmEUlh8JGfDmsDG12m1JDAh0e0huwK_MlyKpdfn22ru3zsm7lYLfBo=@protonmail.com> <30li5MRxkBhzLxLmzRnHkCdn8n3Feqegi-FLZ5VDyIX2uRJfq4kVtrsLxw6dUtsM1atYV25IfIfDaQp4s2Dn2vc8LvYkhbAsn0v_Fwjerpw=@protonmail.com> In-Reply-To: From: Billy Tetrud Date: Tue, 25 May 2021 10:01:51 -1000 Message-ID: To: Erik Aronesty Content-Type: multipart/alternative; boundary="00000000000056d68a05c32d00f8" X-Mailman-Approved-At: Tue, 25 May 2021 20:16:47 +0000 Cc: Bitcoin Protocol Discussion , SatoshiSingh Subject: Re: [bitcoin-dev] Opinion on proof of stake in future X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 May 2021 20:02:16 -0000 --00000000000056d68a05c32d00f8 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable @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 all 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 where 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 mint on old blocks (until and if it becomes the heaviest chain). Because the attacker would need probably >45% of the active stake (take a look at the reasoning here for a deeper analysis of that statement), I don't agree that punishment is not a sufficient mitigation of the nothing at stake problem. To exploit the nothing at stake problem, you basically need to 51% attack, at 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 PoW. > 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 public 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. Note, tho, that quorum-based PoS generally also have punishments as part of the protocol. The introduction of punishments do indeed handily solve the nothing at stake problem. And you didn't mention a single problem that the punishments introduce that weren't already there before punishments. There are tradeoffs with introducing punishments (eg in some cases you might punish honest actors), but they are minor in comparison to solving the nothing at stake problem. So I don't think it is at all misleading to claim that "nothing at stake" is a solved problem. I do in fact mean that the solutions to that problem don't introduce any other problems with anywhere near the same level of significance. On Tue, May 25, 2021 at 3:00 AM Erik Aronesty wrote: > > > you burn them to be used at a future particular block height > > > This sounds exploitable. It seems like an attacker could simply focus > all their burns on a particular set of 6 blocks to double spend, minimizi= ng > their cost of attack. > > could be right. the original idea was to have burns decay over 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 than 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 > wrote: > > > > Is this the kind of proof of burn you're talking about? > > > > > if i have a choice between two chains, one longer and one shorter, = i > can only choose one... deterministically > > > > What prevents you from attempting to mine block 553 on both 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 the 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 height > > > > This sounds exploitable. It seems like an attacker could simply focus > all their burns on a particular set of 6 blocks to double spend, minimizi= ng > their cost of attack. > > > > > i can imagine scenarios where large stakeholders can collude to punis= h > smaller stakeholders simply to drive them out of business, for example > > > > Are you talking about a 51% attack? This is possible in any > decentralized cryptocurrency. > > > > > > On Mon, May 24, 2021 at 11:49 AM Erik Aronesty wrote: > >> > >> > > your burn investment is always "at stake", any redaction can resul= t > in a loss-of-burn, because burns can be tied, precisely, to block-heights > >> > I'm fuzzy on how proof of burn works. > >> > >> when you burn coins, you burn them to be used at a future particular > >> block height: so if i'm burning for block 553, i can only use them to > >> mine block 553. if i have a choice between two chains, one longer > >> and one shorter, i can only choose one... deterministically, for that > >> burn: the chain with the height 553. if we fix the "lead time" for > >> burned coins to be weeks or even months in advance, miners have a very > >> strong, long-term, investment in the stability of the chain. > >> > >> 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 instability always > >> hurt miners the most. > >> > >> the "punishment" systems of PoS are "weird at best", certainly > >> unproven. i can imagine scenarios where large stakeholders 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 system... > >> > >> in PoB, there is no complexity. simpler systems like this are > >> typically more secure. > >> > >> PoB also solves problems caused by "energy dependence", which could > >> lead to state monopolies on mining (like the new Bitcoin Mining > >> Council). these consortiums, if state sanctioned, could become a > >> source of censorship, for example. Since PoB doesn't require 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 interests of > >> existing stakeholders > >> > >> > >> > >> > >> On Mon, May 24, 2021 at 4:44 PM Billy Tetrud > 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 be online. > >> > > >> > > your burn investment is always "at stake", any redaction can resul= t > in a loss-of-burn, because burns can be tied, precisely, to 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, whi= ch > 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-stake > >> > > >> > 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 = is > a solved problem at this point for PoS. > >> > > >> > > >> > > >> > On Mon, May 24, 2021 at 3:47 AM Erik Aronesty wrote: > >> >> > >> >> > I don't see a way to get around the conflicting requirement 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 stake" problem in > your view? > >> >> > >> >> definition of nothing at stake: in the event of a fork, whether the > >> >> fork is accidental or a malicious, the optimal strategy for any min= er > >> >> is to mine on every chain, so that the miner gets their reward no > >> >> matter which fork wins. indeed in proof-of-stake, the proofs are > >> >> published on the very chains mines, so the incentive is magnified. > >> >> > >> >> in proof-of-burn, your burn investment is always "at stake", any > >> >> redaction can result in a loss-of-burn, because burns 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 proof-of-stake, a= nd > >> >> even more secure than proof of work > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > > >> >> > >> >> On Sun, May 23, 2021 at 3:52 AM Lloyd Fournier via bitcoin-dev > >> >> wrote: > >> >> > > >> >> > Hi Billy, > >> >> > > >> >> > I was going to write a post which started by dismissing many of > the weak arguments that are made against PoS made in this thread and > elsewhere. > >> >> > Although I don't agree with all your points you have done a decen= t > job here so I'll focus on the second part: why I think Proof-of-Stake is > inappropriate for a Bitcoin-like system. > >> >> > > >> >> > Proof of stake is not fit for purpose for a global settlement > layer in a pure digital asset (i.e. "digital gold") which is what Bitcoin > is trying to be. > >> >> > PoS necessarily gives responsibilities to the holders of coins > that they do not want and cannot handle. > >> >> > In Bitcoin, large unsophisticated coin holders can put their coin= s > in cold storage without a second thought given to the health of the > underlying ledger. > >> >> > As much as hardcore Bitcoiners try to convince them to run their > own node, most don't, and that's perfectly acceptable. > >> >> > At no point do their personal decisions affect the underlying > consensus -- it only affects their personal security assurance (not that = of > the system itself). > >> >> > In PoS systems this clean separation of responsibilities does not > exist. > >> >> > > >> >> > I think that the more rigorously studied PoS protocols will work > fine within the security claims made in their papers. > >> >> > People who believe that these protocols are destined 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 Ouroboros Praos[3] with > an inbuilt on-chain delegation system[5]. > >> >> > In these protocols, coin holders who do not want to run their nod= e > 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 there 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 purchased 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 profit 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 dishonest 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 delegating to another > pool...oh wait I guess that might be censored too! This seems really real= ly > bad. > >> >> > In Bitcoin, miners can just join a different pool at a whim. Ther= e > is nothing the attacker can do to stop them. A temporary dishonest majori= ty > heals relatively well. > >> >> > > >> >> > There is another severe disadvantage to this on-chain delegation > system: every UTXO must indicate which staking account this UTXO belongs = to > so the appropriate share of block rewards can be transferred 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 significantly. > >> >> > > >> >> > ### "Pure" proof of stake (Algorand) > >> >> > > >> >> > Algorand's[4] approach is to only allow online stake 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 coin holding keys > online so in Alogorand you can authorize a set of "participation 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 malicious party with = a > nice website (see random example [2]) offering you a good return. > >> >> > Damn it's still Proof-of-SquareSpace! > >> >> > The minor advantage is that at least the participation keys expir= e > after a certain amount of time so eventually the SquareSpace attacker wil= l > lose their hold on consensus. > >> >> > Importantly there is also less junk on the blockchain 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 requirement 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 social attack surfac= e > 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 responsibilities for > the holder of the coin. > >> >> > After all, gold is an inert element on the periodic 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 more 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 being able to s= ay > it uses less electricity. It goes without saying that making bad technica= l > decisions to appease the current political climate is an anathema to > Bitcoin. > >> >> > > >> >> > Would be interested to know if you or others think differently on > these points. > >> >> > > >> >> > [1]: > https://developer.algorand.org/docs/run-a-node/participate/generate_keys/ > >> >> > [2]: https://staking.staked.us/algorand-staking > >> >> > [3]: https://eprint.iacr.org/2017/573.pdf > >> >> > [4]: > https://algorandcom.cdn.prismic.io/algorandcom%2Fece77f38-75b3-44de-bc7f-= 805f0e53a8d9_theoretical.pdf > >> >> > [5]: > https://hydra.iohk.io/build/790053/download/1/delegation_design_spec.pdf > >> >> > > >> >> > Cheers, > >> >> > > >> >> > LL > >> >> > > >> >> > On Fri, 21 May 2021 at 19:21, Billy Tetrud via bitcoin-dev < > bitcoin-dev@lists.linuxfoundation.org> wrote: > >> >> >> > >> >> >> 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 succe= ss > 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 P= oS > 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 i= s > a proof of stake consensus protocol we could build that has substantially > higher security (cost / capital required to execute an attack) while at t= he > 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 disagreement= s > 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) affec= t > 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 fractio= n > 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 n= o > 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. Bot= h > 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 =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 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 requiremen= t. > 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 be= st > proof of work can do is require an attacker to obtain 33% of the hashpowe= r > because of the selfish mining 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) = =E2=80=94 > specifically the famous "security vs. liveness" guarantee > >> >> >> > >> >> >> Do you have a good source that talks about why you think proof o= f > 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 everyon= e > 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-de= v > 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 actual= ly > 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 worki= ng > >> >> >>>>> 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 som= e > 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 securi= ty > >> >> >>>>> 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 wa= s > >> >> >>>>> 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 sav= e > energy, but solely as a means to make the time between blocks more consta= nt. > >> >> >>>>> > > >> >> >>>>> > 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 instanc= e > 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-de= v > >> >> >>>> > >> >> >>>> > >> >> >>>> > >> >> >>>> -- > >> >> >>>> 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/listinfo/bitcoin-dev > >> >> >> > >> >> >> _______________________________________________ > >> >> >> bitcoin-dev mailing list > >> >> >> bitcoin-dev@lists.linuxfoundation.org > >> >> >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > >> >> > > >> >> > _______________________________________________ > >> >> > bitcoin-dev mailing list > >> >> > bitcoin-dev@lists.linuxfoundation.org > >> >> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > --00000000000056d68a05c32d00f8 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
@befreeandopen " An attacker can calculate whether or not she can prolong this chain or not = and if so with what timestamp."

The scenario yo= u describe would only be likely to happen at all 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 prob= lem. The nothing at stake problem is the problem where anyone will mint on = any chain. Its clear that if there's a substantial punishment for minti= ng 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 mint on old blocks (= until and if it becomes the heaviest chain). Because the attacker would nee= d probably >45% of the active stake (take a look at the reasoning here for a deeper analysis of that statement), I do= n't agree that punishment=C2=A0is not a sufficient mitigation of the no= thing at stake problem. To exploit the nothing at stake problem, you basica= lly need to 51% attack, at which point you've exceeded the operating co= nditions of the system, so of course its gonna have problems, just like a 5= 1% attack would cause with PoW.

> I am not sure= if this is what you call quorum-based PoS

Yes, pr= e-selected minters is exactly what I mean by that.

> it allows the attacker to know who to attack at which point with powe= rful DDOS in order to hurt liveness of such system

Just like in bitcoin, associating keys with IP addresses isn't general= ly an easy thing to do on the fly like that. If you know someone's IP a= ddress, you can target them. But if you only know their address or public k= ey, 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.=C2=A0

Note, tho, that qu= orum-based PoS generally also have punishments as part of the protocol. The= introduction of punishments do indeed handily solve the nothing at stake p= roblem. And you didn't mention a single problem that the punishments in= troduce that weren't already there before punishments. There are tradeo= ffs with introducing punishments (eg in some cases you might punish honest = actors), but they are minor in comparison to solving the nothing at stake p= roblem.

So I don't think it is at all misleadi= ng to claim that "nothing at stake" is a solved problem. I do in = fact mean that the solutions to that problem don't introduce any other = problems with anywhere near the same level of significance.=C2=A0

On T= ue, May 25, 2021 at 3:00 AM Erik Aronesty <erik@q32.com> wrote:
> > you burn them to be used at a future particular bl= ock height

> This sounds exploitable. It seems like an attacker could simply focus = all their burns on a particular set of 6 blocks to double spend, minimizing= their cost of attack.

could be right.=C2=A0 =C2=A0the original idea was to have burns decay over = 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 than 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@gmail.com> wrote:
>
> Is this the kind of proof of burn you're talking about?
>
> >=C2=A0 =C2=A0if i have a choice between two chains, one longer and= one shorter, i can only choose one... deterministically
>
> What prevents you from attempting to mine block 553 on both 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 the chain i= s a common good, and the tragedy of the commons holds for it.
>
> > you burn them to be used at a future particular block height
>
> This sounds exploitable. It seems like an attacker could simply focus = all their burns on a particular set of 6 blocks to double spend, minimizing= their cost of attack.
>
> > i can imagine scenarios where large stakeholders can collude to p= unish smaller stakeholders simply to drive them out of business, for exampl= e
>
> Are you talking about a 51% attack? This is possible in any decentrali= zed cryptocurrency.
>
>
> On Mon, May 24, 2021 at 11:49 AM Erik Aronesty <erik@q32.com> wrote:
>>
>> > > your burn investment is always "at stake", any= redaction can result in a loss-of-burn, because burns can be tied, precise= ly, to block-heights
>> > I'm fuzzy on how proof of burn works.
>>
>> when you burn coins, you burn them to be used at a future particul= ar
>> block height: so if i'm burning for block 553, i can only use = them to
>> mine block 553.=C2=A0 =C2=A0if i have a choice between two chains,= one longer
>> and one shorter, i can only choose one... deterministically, for t= hat
>> burn: the chain with the height 553.=C2=A0 =C2=A0if we fix the &qu= ot;lead time" for
>> burned coins to be weeks or even months in advance, miners have a = very
>> strong, long-term, investment in the stability of the chain.
>>
>> therefore there is no "nothing at stake" problem.=C2=A0 = =C2=A0it's
>> deterministic, so miners have no choice.=C2=A0 they can *only* cho= ose the
>> transactions that go into the block.=C2=A0 they cannot choose whic= h chain
>> to mine, and it's time-locked, so rollbacks and instability al= ways
>> hurt miners the most.
>>
>> the "punishment" systems of PoS are "weird at best&= quot;, certainly
>> unproven.=C2=A0 =C2=A0i can imagine scenarios where large stakehol= ders can
>> collude to punish smaller stakeholders simply to drive them out of=
>> business, for example.=C2=A0 =C2=A0and then you have to put checks= in place to
>> prevent that, and more checks for those prevention system...
>>
>> in PoB, there is no complexity.=C2=A0 simpler systems like this ar= e
>> typically more secure.
>>
>> PoB also solves problems caused by "energy dependence", = which could
>> lead to state monopolies on mining (like the new Bitcoin Mining >> Council).=C2=A0 =C2=A0these consortiums, if state sanctioned, coul= d become a
>> source of censorship, for example.=C2=A0 =C2=A0Since PoB doesn'= ;t require 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 interests of
>> existing stakeholders
>>
>>
>>
>>
>> On Mon, May 24, 2021 at 4:44 PM Billy Tetrud <billy.tetrud@gmail.com> w= rote:
>> >
>> > >=C2=A0 proof of burn clearly solves this, since nothing i= s 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 be on= line.
>> >
>> > > your burn investment is always "at stake", any= redaction can result in a loss-of-burn, because burns can be tied, precise= ly, to block-heights
>> >
>> > So you're saying that if say someone tries to mine a bloc= k on a shorter chain, that requires them to send a transaction burning thei= r coins, and that transaction could also be spent on the longest chain, whi= ch means their coins are burned even if the chain they tried to mine on doe= sn't win? I'm fuzzy on how proof of burn works.
>> >
>> > > proof of burn can be more secure than proof-of-stake
>> >
>> > FYI, proof of stake can be done without the "nothing at = stake" problem. You can simply punish people who mint on shorter chain= s (by rewarding people who publish proofs of this happening on the main cha= in). 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&quo= t; problem is a solved problem at this point for PoS.
>> >
>> >
>> >
>> > On Mon, May 24, 2021 at 3:47 AM Erik Aronesty <erik@q32.com> wrote:
>> >>
>> >> > I don't see a way to get around the conflicting = requirement 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.<= br> >> >>
>> >> proof of burn clearly solves this, since nothing is held = online
>> >>
>> >> >=C2=A0 how does proof of burn solve the "nothing= at stake" problem in your view?
>> >>
>> >> definition of nothing at stake: in the event of a fork, w= hether the
>> >> fork is accidental or a malicious, the optimal strategy f= or any miner
>> >> is to mine on every chain, so that the miner gets their r= eward no
>> >> matter which fork wins.=C2=A0 =C2=A0indeed in proof-of-st= ake, the proofs are
>> >> published on the very chains mines, so the incentive is m= agnified.
>> >>
>> >> in proof-of-burn, your burn investment is always "at= stake", any
>> >> redaction can result in a loss-of-burn, because burns can= be tied,
>> >> precisely, to block-heights
>> >>
>> >> as a result, miners no longer have an incentive to mine a= ll chains
>> >>
>> >> in this way proof of burn can be more secure than proof-o= f-stake, and
>> >> even more secure than proof of work
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> >
>> >>
>> >> On Sun, May 23, 2021 at 3:52 AM Lloyd Fournier via bitcoi= n-dev
>> >> <bitcoin-dev@lists.linuxfoundation.org> wrote:<= br> >> >> >
>> >> > Hi Billy,
>> >> >
>> >> > I was going to write a post which started by dismiss= ing many of the weak arguments that are made against PoS made in this threa= d and elsewhere.
>> >> > Although I don't agree with all your points you = have done a decent job here so I'll focus on the second part: why I thi= nk Proof-of-Stake is inappropriate for a Bitcoin-like system.
>> >> >
>> >> > Proof of stake is not fit for purpose for a global s= ettlement layer in a pure digital asset (i.e. "digital gold") whi= ch is what Bitcoin is trying to be.
>> >> > PoS necessarily gives responsibilities to the holder= s of coins that they do not want and cannot handle.
>> >> > In Bitcoin, large unsophisticated coin holders can p= ut their coins in cold storage without a second thought given to the health= of the underlying ledger.
>> >> > As much as hardcore Bitcoiners try to convince them = to run their own node, most don't, and that's perfectly acceptable.=
>> >> > At no point do their personal decisions affect the u= nderlying consensus -- it only affects their personal security assurance (n= ot that of the system itself).
>> >> > In PoS systems this clean separation of responsibili= ties does not exist.
>> >> >
>> >> > I think that the more rigorously studied PoS protoco= ls will work fine within the security claims made in their papers.
>> >> > People who believe that these protocols are destined= 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 Ouroboros = Praos[3] with an inbuilt on-chain delegation system[5].
>> >> > 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&= quot;.
>> >> > I call the resulting system Proof-of-SquareSpace sin= ce most will choose a pool by looking around for one with a nice website an= d offering the largest share of the block reward.
>> >> > On the surface this might sound no different than so= meone with an mining rig shopping around for a good mining pool but there a= re crucial differences:
>> >> >
>> >> > 1. The person making the decision is forced into it = just because they own the currency -- someone with a mining rig has purchas= ed 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 profit = variance. You still see every block that you help create and *you never hel= p create a block without seeing it first*.
>> >> >
>> >> > 3. If by SquareSpace sybil attack you gain a dishone= st majority and start censoring transactions how are the users meant to red= elegate their stake to honest pools?
>> >> > I guess they can just send a transaction delegating = to another pool...oh wait I guess that might be censored too! This seems re= ally 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 temporary dis= honest majority heals relatively well.
>> >> >
>> >> > There is another severe disadvantage to this on-chai= n delegation system: every UTXO must indicate which staking account this UT= XO belongs to so the appropriate share of block rewards can be transferred = there.
>> >> > Being able to associate every UTXO to an account rui= ns one of the main privacy advantages of the UTXO model.
>> >> > It also grows the size of the blockchain significant= ly.
>> >> >
>> >> > ### "Pure" proof of stake (Algorand)
>> >> >
>> >> > Algorand's[4] approach is to only allow online s= take to participate in the protocol.
>> >> > Theoretically, This means that keys holding funds ha= ve to be online in order for them to author blocks when they are chosen. >> >> > Of course in reality no one wants to keep their coin= holding keys online so in Alogorand you can authorize a set of "parti= cipation keys"[1] that will be used to create blocks on your coin hold= ing key's behalf.
>> >> > Hopefully you've spotted the problem.
>> >> > You can send your participation keys to any maliciou= s party with a nice website (see random example [2]) offering you a good re= turn.
>> >> > Damn it's still Proof-of-SquareSpace!
>> >> > The minor advantage is that at least the participati= on keys expire after a certain amount of time so eventually the SquareSpace= attacker will lose their hold on consensus.
>> >> > Importantly there is also less junk on the blockchai= n because the participation keys are delegated off-chain and so are not mak= ing as much of a mess.
>> >> >
>> >> > ### Conclusion
>> >> >
>> >> > I don't see a way to get around the conflicting = requirement 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.<= br> >> >> > If we allow delegation then we open up a new social = attack surface and it degenerates to Proof-of-SquareSpace.
>> >> >
>> >> > For a "digital gold" like system like Bitc= oin we optimize for simplicity and desperately want to avoid extraneous res= ponsibilities for the holder of the coin.
>> >> > After all, gold is an inert element on the periodic = table that doesn't confer responsibilities on the holder to maintain th= e quality of all the other bars of gold out there.
>> >> > Bitcoin feels like this too and in many ways is more= inert and beautifully boring than gold.
>> >> > For Bitcoin to succeed I think we need to keep it th= at 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 bein= g able to say it uses less electricity. It goes without saying that making = bad technical decisions to appease the current political climate is an anat= hema to Bitcoin.
>> >> >
>> >> > Would be interested to know if you or others think d= ifferently on these points.
>> >> >
>> >> > [1]: https://developer.algorand.org/docs/run-a-node/participate/generate_keys/<= /a>
>> >> > [2]: https://staking.staked.us/algo= rand-staking
>> >> > [3]: https://eprint.iacr.org/2017/573.pdf=
>> >> > [4]: https://algorandcom.cdn.prismic.io/algorandcom= %2Fece77f38-75b3-44de-bc7f-805f0e53a8d9_theoretical.pdf
>> >> > [5]: = https://hydra.iohk.io/build/790053/download/1/delegation_design_spec.pdf
>> >> >
>> >> > Cheers,
>> >> >
>> >> > LL
>> >> >
>> >> > On Fri, 21 May 2021 at 19:21, Billy Tetrud via bitco= in-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
>> >> >>
>> >> >> I think there is a lot of misinformation and bia= s against Proof of Stake. Yes there have been lots of shady coins that use = insecure PoS mechanisms. Yes there have been massive issues with distributi= on of PoS coins (of course there have also been massive issues with PoW coi= ns as well). However, I want to remind everyone that there is a difference = between "proved to be impossible" and "have not achieved rec= ognized 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 experime= nt with bitcoin by switching to PoS, but from my research, it seems very li= kely that there is a proof of stake consensus protocol we could build that = has substantially higher security (cost / capital required to execute an at= tack) while at the same time costing far less resources (which do translate= to fees on the network) *without* compromising any of the critical securit= y properties bitcoin relies on. I think the critical piece of this is the d= isagreements around hardcoded checkpoints, which is a critical piece solvin= g attacks that could be levied on a PoS chain, and how that does (or doesn&= #39;t) affect the security model.
>> >> >>
>> >> >> @Eric Your proof of stake fallacy seems to be sa= ying that PoS is worse when a 51% attack happens. While I agree, I think th= at 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 th= e 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 t= hat 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 mo= re than 10x. By contrast, proof of work does in fact have clear centralizat= ion pressure - this is not disputed. Our goal in relation to that is to ens= ure that the centralization pressure remains insignifiant. Proof of work al= so 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 wors= e 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 =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 link= ed to. I'm not aware of any proof that all PoS systems have a failure t= hreshold of 1/3. I know that staking systems like Casper do in fact have th= at 1/3 requirement. However there are PoS designs that should exceed that u= p to nearly 50% as far as I'm aware. Proof of work is not in fact resil= ient up to the 1/2 threshold in the way you would think. IE, if 100% of min= ers are currently honest and have a collective 100 exahashes/s hashpower, a= n 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 incr= eases 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 discussed in depth in this p= aper: https://arxiv.org/abs/1311.0243. Together, both of these th= ings reduce PoW's security by a factor of about 83% (1 - 50%*33%).
>> >> >>
>> >> >>=C2=A0 > Proof of Stake requires other trade-o= ffs which 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 y= ou think proof of stake cannot be used for a trustless digital cash?
>> >> >>
>> >> >> > You cannot gain tokens without someone choo= sing 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&q= uot; of one of millions of people in the market can be reasonably considere= d 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 Dubrovsk= y via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:<= br> >> >> >>>
>> >> >>> Ah sorry, I didn't realize this was, in = fact, a different thread! :)
>> >> >>>
>> >> >>> On Wed, May 19, 2021 at 10:07 AM Michael Dub= rovsky <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 wo= uld 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 securit= y assumptions of Hashcash and actually contains SHA (can be SHA3, SHA256, e= tc hash is interchangeable).
>> >> >>>>
>> >> >>>> Cheers,
>> >> >>>> Mike
>> >> >>>>
>> >> >>>> On Tue, May 18, 2021 at 4:55 PM Erik Aro= nesty via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wro= te:
>> >> >>>>>
>> >> >>>>> 1. i never suggested vdf's to re= place pow.
>> >> >>>>>
>> >> >>>>> 2. my suggestion was specifically *i= n the context of* a working
>> >> >>>>> proof-of-burn protocol
>> >> >>>>>
>> >> >>>>> - vdfs used only for timing (not blo= ck height)
>> >> >>>>> - blind-burned coins of a specific a= ge 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 mi= mic, in every meaningful way, the
>> >> >>>>> value gained from proof of work... w= ithout 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)<= br> >> >> >>>>> - 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* tha= t 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 wor= thwhile, a test net could be spun
>> >> >>>>> up, and a hard-fork could be initiat= ed.
>> >> >>>>>
>> >> >>>>> 4. i would never suggest such a thin= g unless i believed it was
>> >> >>>>> possible that consensus was possible= .=C2=A0 so no, this is not an "alt
>> >> >>>>> coin"
>> >> >>>>>
>> >> >>>>> On Tue, May 18, 2021 at 10:02 AM Zac= Greenwood <zachg= rw@gmail.com> wrote:
>> >> >>>>> >
>> >> >>>>> > Hi ZmnSCPxj,
>> >> >>>>> >
>> >> >>>>> > Please note that I am not sugge= sting VDFs as a means to save energy, but solely as a means to make the tim= e between blocks more constant.
>> >> >>>>> >
>> >> >>>>> > Zac
>> >> >>>>> >
>> >> >>>>> >
>> >> >>>>> > On Tue, 18 May 2021 at 12:42, Z= mnSCPxj <Zm= nSCPxj@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 take= s say 9 minutes to resolve (VDF being subject to difficulty adjustments sim= ilar to the as-is). As per the property of VDFs, miners are able show proof= of work.
>> >> >>>>> >> >
>> >> >>>>> >> > 2. Use current PoW mec= hanism 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 sequ= ential 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 an= d even *more* energy consumption.
>> >> >>>>> >> After all, if you can start= mining 0.1s faster than the competition, that is a 0.1s advantage where *o= nly you* can mine *in the entire world*.
>> >> >>>>> >>
>> >> >>>>> >> Regards,
>> >> >>>>> >> ZmnSCPxj
>> >> >>>>> ____________________________________= ___________
>> >> >>>>> bitcoin-dev mailing list
>> >> >>>>> bitcoin-dev@lists.linuxfoundation.or= g
>> >> >>>>> 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/listinfo/bitcoin-dev
>> >> >>
>> >> >> _______________________________________________<= br> >> >> >> bitcoin-dev mailing list
>> >> >> bitcoin-dev@lists.linuxfoundation.org
>> >> >> https://lis= ts.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>> >> >
>> >> > _______________________________________________
>> >> > bitcoin-dev mailing list
>> >> > bitcoin-dev@lists.linuxfoundation.org
>> >> > https://lists.l= inuxfoundation.org/mailman/listinfo/bitcoin-dev
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