Good morning Dan,My understanding is that it is impossible for soft forks to be prevented.1. Anyone-can-spendThere are a very large number of anyone-can-spend scripts, and it would be very impractical to ban them all.For example, the below output script is anyone-can-spend<random number> OP_TRUESo is the below:OP_SIZE <random small number> OP_EQUALOr:OP_1ADD <random number> OP_EQUALOr:OP_BOOLANDOr:OP_BOOLORAnd so on.So no, it is not practically possible to ban anyone-can-spend outputs, as there are too many potential scriptPubKey that anyone can spend.It is even possible to have an output that requires a proof-of-work, like so:OP_HASH256 <difficulty target> OP_LESSTHANAll the above outputs are disallowed from propagation by IsStandard, but a miner can put them validly in a block, and IsStandard is not consensus code and can be modified.2. Soft fork = restrictIt is possible (although unlikely) for a majority of miners to run soft forking code which the rest of us are not privy to.For example, for all we know, miners are already blacklisting spends on Satoshi's coins. We would not be able to detect this at all, since no transaction that spends Satoshi's coins have been broadcast, ever. It is thus indistinguishable from a world where Satoshi lost his private keys. Of course, the world where Satoshi never spent his coins and miners are blacklisting Satoshi's coins, is more complex than the world where Satoshi never spent his coins, so it is more likely that miners are not blacklisting.But the principle is there. We may already be in a softfork whose rules we do not know, and it just so happens that all our transactions today do not violate those rules. It is impossible for us to know this, but it is very unlikely.Soft forks apply further restrictions on Bitcoin. Hard forks do not. Thus, if everyone else is entering a soft fork and we are oblivious, we do not even know about it. Whereas, if everyone else is entering a hard fork, we will immediately see (and reject) invalid transactions and blocks.Thus the only way to prevent soft fork is to hard fork against the new soft fork, like Bcash did.Regards,ZmnSCPxj-------- Original Message --------Subject: [bitcoin-dev] hypothetical: Could soft-forks be prevented?Local Time: September 13, 2017 5:50 PMUTC Time: September 13, 2017 9:50 AMTo: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org >Hi, I am interested in the possibility of a cryptocurrency software(future bitcoin or a future altcoin) that strives to have immutableconsensus rules.The goal of such a cryptocurrency would not be to have the latest andgreatest tech, but rather to be a long-term store of value and to offerinvestors great certainty and predictability... something that marketstend to like. And of course, zero consensus rule changes also meansless chance of new bugs and attack surface remains the same, which isgood for security.Of course, hard-forks are always possible. But that is a clear splitand something that people must opt into. Each party has to make achoice, and inertia is on the side of the status quo. Whereassoft-forks sort of drag people along with them, even those who opposethe changes and never upgrade. In my view, that is problematic,especially for a coin with permanent consensus rule immutability as agoal/ethic.As I understand it, bitcoin soft-forks always rely on anyone-can-spendtransactions. If those were removed, would it effectively preventsoft-forks, or are there other possible mechanisms? How important areany-one-can spend tx for other uses?More generally, do you think it is possible to programmaticallyavoid/ban soft-forks, and if so, how would you go about it?_______________________________________________ bitcoin-dev mailing list
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