The presumption of the mining aspect of the Bitcoin security model is that the 
mining majority is a broadly distributed set of independent people, not one 
person who controls a majority of the hash power. 

You seem to have overlooked a qualifier in your Satoshi quote: "...by nodes 
that are not cooperating to attack the network". A single miner with majority 
hash power is of course cooperating with himself. At that point the question of 
whether he is attacking the network is moot, it's his network.

I believe that Pieter's point is that a system optimized for orphan rate may in 
effect be optimized for a single entity providing all double spend protection. 
That works directly against the central principle of Bitcoin security. The 
security of the money is a function of the number of independent miners and 
sellers.

e

> On Dec 10, 2016, at 7:17 PM, Daniele Pinna via bitcoin-dev 
> <[email protected]> wrote:
> 
> How is the adverse scenario you describe different from a plain old 51% 
> attack? Each proposed protocol change  where 51% or more  of the network can 
> potentially game the rules and break the system should be considered just as 
> acceptable/unacceptable as another. 
> 
> There comes a point where some form of basic honesty must be assumed on 
> behalf of participants benefiting from the system working properly and 
> reliably. 
> 
> Afterall, what magic line of code prohibits all miners from simultaneously 
> turning all their equipment off...  just because? 
> 
> Maybe this 'one':
> 
> "As long as a majority of CPU power is controlled by nodes that are not 
> cooperating to attack the network, they'll generate the longest chain and 
> outpace attackers. The network itself requires minimal structure."
> 
> Is there such a thing as an unrecognizable 51% attack?  One where the 
> remaining 49% get dragged in against their will? 
> 
> Daniele 
> 
>> On Dec 10, 2016 6:39 PM, "Pieter Wuille" <[email protected]> wrote:
>>> On Sat, Dec 10, 2016 at 4:23 AM, Daniele Pinna via bitcoin-dev 
>>> <[email protected]> wrote:
>>> We have models for estimating the probability that a block is orphaned 
>>> given average network bandwidth and block size. 
>>> 
>>> The question is, do we have objective measures of these two quantities? 
>>> Couldn't we target an orphan_rate < max_rate? 
>> 
>> Models can predict orphan rate given block size and network/hashrate 
>> topology, but you can't control the topology (and things like FIBRE hide the 
>> effect of block size on this as well). The result is that if you're purely 
>> optimizing for minimal orphan rate, you can end up with a single 
>> (conglomerate of) pools producing all the blocks. Such a setup has no 
>> propagation delay at all, and as a result can always achieve 0 orphans.
>> 
>> Cheers,
>> 
>> -- 
>> Pieter
>> 
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