True however in principle a soft-fork can also be soft-forked out. Eg say a publicly known soft-fork done by miners only that user node software did not upgrade for first by opt-in adoption. If there was consensus against by users and ecosystem a node/user flag day soft fork could block it's effects. Or if a soft fork was determined to have a major bug.
However most types of soft fork are opt-in and so mostly that situation seems unlikely. A censorship soft-fork is harder, that's a standard hard-fork to bypass with current fungibility mechanisms. Adam On Sep 15, 2017 08:12, "ZmnSCPxj via bitcoin-dev" < bitcoin-dev@lists.linuxfoundation.org> wrote: > Good morning Dan, > > My understanding is that it is impossible for soft forks to be prevented. > > 1. Anyone-can-spend > > There 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_TRUE > > So is the below: > > OP_SIZE <random small number> OP_EQUAL > > Or: > > OP_1ADD <random number> OP_EQUAL > > Or: > > OP_BOOLAND > > Or: > > OP_BOOLOR > > And 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_LESSTHAN > > All 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 = restrict > > It 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 PM > UTC Time: September 13, 2017 9:50 AM > From: bitcoin-dev@lists.linuxfoundation.org > To: 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 immutable > consensus rules. > > The goal of such a cryptocurrency would not be to have the latest and > greatest tech, but rather to be a long-term store of value and to offer > investors great certainty and predictability... something that markets > tend to like. And of course, zero consensus rule changes also means > less chance of new bugs and attack surface remains the same, which is > good for security. > > Of course, hard-forks are always possible. But that is a clear split > and something that people must opt into. Each party has to make a > choice, and inertia is on the side of the status quo. Whereas > soft-forks sort of drag people along with them, even those who oppose > the changes and never upgrade. In my view, that is problematic, > especially for a coin with permanent consensus rule immutability as a > goal/ethic. > > As I understand it, bitcoin soft-forks always rely on anyone-can-spend > transactions. If those were removed, would it effectively prevent > soft-forks, or are there other possible mechanisms? How important are > any-one-can spend tx for other uses? > > More generally, do you think it is possible to programmatically > avoid/ban soft-forks, and if so, how would you go about it? > > > > > > _______________________________________________ > 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 > >
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