đź“… Original date posted:2015-09-19
đź“ť Original message:We need to distinguish between two different things here:
1) A 51% attack, where the majority of mining power is *malicious* (hence “attack”)
and
2) A fork that exists because of a disagreement in the network, with total mining power split in two camps, each camp mining peacefully on their own chain
These are two very different scenarios.
Some claim that including the UTXO set hash in the block creates a vulnerability where miners can include the wrong UTXO hash, and mine on that, but this is only possible if a 51% attack is in effect. And if a 51% attack is in effect, it’s a moot point, because Bitcoin is useless anyway, because that 51% malicious mining power could just as well be used for mining empty blocks on top of the official chain. Or blocks containing randomly generated transactions, without confirming any legitimate transactions. This is why we say that a majority of honest miners is a hard requirement for Bitcoin. A majority of dishonest miners can only be circumvented through centralisation, and then we don’t have Bitcoin any longer.
Scenario 2 is unproblematic regardless of whether we include the UTXO hash in the block (and make it consensus-critical) or not, since the majority mining power on either chain isn’t malicious.
It is correct that if you’re a full node, and a 51% attack is in effect, you are able to verify that miners are honest (ie. you know whether a 51% attack is in effect or not). But this doesn’t change the fact that the Bitcoin network is unreliable, at best, when a majority of mining power is used for malicious purposes.
/Rune
> On 19 Sep 2015, at 04:30, Justus Ranvier via bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org> wrote:
>
> On 18/09/15 15:17, Rune Kjær Svendsen via bitcoin-dev wrote:
>> Bitcoin does not function if the majority of mining power is dishonest. There is no way around that. It’s how proof-of-work functions.
>
>
> None of those statements are true.
>
> If a majority of Bitcoin miners are mining invalid blocks, then they
> aren't Bitcoin miners any more and are no longer relevant to the Bitcoin
> consensus.
>
> There does exist a problem that light clients aren't always able to tell
> the difference between chains that are valid and chains that are not
> valid, but it's is possible to create simple proofs that would do so:
>
> https://gist.github.com/justusranvier/451616fa4697b5f25f60
>
>
> If those changes would be implemented, then any node that knew a chain
> was invalid could produce a compact proof that anyone else in the
> network could verify, regardless of how much proof of work was used to
> create the invalid chain.
>
> Committed UTXO sets would need safe to rely upon if a similar set of
> proofs that a particular set was invalid existed.
>
> --
> Justus Ranvier
> Open Bitcoin Privacy Project
> http://www.openbitcoinprivacyproject.org/
> justus at openbitcoinprivacyproject.org
> E7AD 8215 8497 3673 6D9E 61C4 2A5F DA70 EAD9 E623
> <0xEAD9E623.asc>_______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Rune Kjær Svendsen [ARCHIVE] /
npub1ss…k53fg
2023-06-07 17:40:59
in reply to nevent1q…478j
Author Public Key
npub1ssutaataqhl7xxp4lw6jutuhfuq5x48cf0xsxpgsxdkxkf9rl9wqnk53fgPublished at
2023-06-07 17:40:59Event JSON
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"content": "📅 Original date posted:2015-09-19\n📝 Original message:We need to distinguish between two different things here:\n\n1) A 51% attack, where the majority of mining power is *malicious* (hence “attack”)\n\nand\n\n2) A fork that exists because of a disagreement in the network, with total mining power split in two camps, each camp mining peacefully on their own chain\n\nThese are two very different scenarios.\n\nSome claim that including the UTXO set hash in the block creates a vulnerability where miners can include the wrong UTXO hash, and mine on that, but this is only possible if a 51% attack is in effect. And if a 51% attack is in effect, it’s a moot point, because Bitcoin is useless anyway, because that 51% malicious mining power could just as well be used for mining empty blocks on top of the official chain. Or blocks containing randomly generated transactions, without confirming any legitimate transactions. This is why we say that a majority of honest miners is a hard requirement for Bitcoin. A majority of dishonest miners can only be circumvented through centralisation, and then we don’t have Bitcoin any longer.\n\nScenario 2 is unproblematic regardless of whether we include the UTXO hash in the block (and make it consensus-critical) or not, since the majority mining power on either chain isn’t malicious.\n\nIt is correct that if you’re a full node, and a 51% attack is in effect, you are able to verify that miners are honest (ie. you know whether a 51% attack is in effect or not). But this doesn’t change the fact that the Bitcoin network is unreliable, at best, when a majority of mining power is used for malicious purposes.\n\n\n\n/Rune\n\n\n\u003e On 19 Sep 2015, at 04:30, Justus Ranvier via bitcoin-dev \u003cbitcoin-dev at lists.linuxfoundation.org\u003e wrote:\n\u003e \n\u003e On 18/09/15 15:17, Rune Kjær Svendsen via bitcoin-dev wrote:\n\u003e\u003e Bitcoin does not function if the majority of mining power is dishonest. There is no way around that. It’s how proof-of-work functions.\n\u003e \n\u003e \n\u003e None of those statements are true.\n\u003e \n\u003e If a majority of Bitcoin miners are mining invalid blocks, then they\n\u003e aren't Bitcoin miners any more and are no longer relevant to the Bitcoin\n\u003e consensus.\n\u003e \n\u003e There does exist a problem that light clients aren't always able to tell\n\u003e the difference between chains that are valid and chains that are not\n\u003e valid, but it's is possible to create simple proofs that would do so:\n\u003e \n\u003e https://gist.github.com/justusranvier/451616fa4697b5f25f60\n\u003e \n\u003e \n\u003e If those changes would be implemented, then any node that knew a chain\n\u003e was invalid could produce a compact proof that anyone else in the\n\u003e network could verify, regardless of how much proof of work was used to\n\u003e create the invalid chain.\n\u003e \n\u003e Committed UTXO sets would need safe to rely upon if a similar set of\n\u003e proofs that a particular set was invalid existed.\n\u003e \n\u003e -- \n\u003e Justus Ranvier\n\u003e Open Bitcoin Privacy Project\n\u003e http://www.openbitcoinprivacyproject.org/\n\u003e justus at openbitcoinprivacyproject.org\n\u003e E7AD 8215 8497 3673 6D9E 61C4 2A5F DA70 EAD9 E623\n\u003e \u003c0xEAD9E623.asc\u003e_______________________________________________\n\u003e bitcoin-dev mailing list\n\u003e bitcoin-dev at lists.linuxfoundation.org\n\u003e https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev",
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