[Bitcoin-segwit2x] Strong 2-Way Replay Protection

hubert maslin hubert.maslin at gmail.com
Mon Oct 9 16:58:19 UTC 2017


Hello Mike, I understand that you're meaning well and want, as we all do,
bitcoin to succeed over long term, and by reading your messages on this
thread I've once again noticed that the current rift within the Bitcoin
community actually springs from a few disagreements that have more to do
with culture and process rather than with long term goals. I'm going to
talk about those disagreements and hopefully state the "pro
decentralisation" position in a way that's conducive to intelligent debate
and perhaps, ultimate agreement.

We want to bring Bitcoin to more users because it has unique features and
qualities (namely permissionless-ness, resistance to tx censorship,
resistance to inflation, pseudonymity) that the existing financial system
doesn't offer. The presence of these features is contrary to the interests
of many powerful entities (the legacy banking system, governments and their
surveillance agencies) and only survive thanks to Bitcoin's
decentralisation and absence of centralised points of failure. Being
willing to sacrifice or endanger Bitcoin's decentralisation to achieve
scaling isn't wise or forward thinking, and is completely self-defeating.
What's the point of on-boarding an ever greater number of users if you run
the risk of weakening those features and give those users the same
experience than current centralised paiement systems offer, e.g. tx
censorship, vulnerability to inflation, and government surveillance? This
would be a nonsensical and unproductive thing to do.

Doing this would be all the more absurd that we now know (as we have since
2015) that, before increasing base block size, we can greatly increase
throughput through more efficient of block space (with Segwit and, in the
near future, with MAST, Schnorr signatures and signatures aggregation) and
more importantly, with second layer technologies such as the Lightning
Network or sidechains. These technologies are under rapid development, and
will soon alleviate scaling.

Presenting the scaling debate as a dichotomy between "onboard users fast
and break things" and "let's for ever stay a store of value for rich
people" is a mistake, because we know we can already greatly improve
scaling, within the next few months and years. Was scaling slower than
anticipated, we should err on the side of caution, and not give our
potential adversaries any lever that they might pull to weaken those
features.

And this is why this scheduled hard fork worries me. Regardless of the
blockchain bloating issue, changing consensus rules without wide community
consensus - and in particular without the consensus of the community
members that value decentralisation and privacy the most - is precisely
such a lever for governments or other antagonists to pull.
It would set an extremely bad precedent. The particulars of this fork -
the fact that it doesn't have replay protection, that it lays a claim on
the Bitcoin brand, that it relies on the imperfect security models of SPV
wallets to make them follow new consensus rules - make things worse.

if this fork is successful and the entire community shifts to the S2X chain
(which, barring a prolonged 51% attack on the original chain, seems
extremely unlikely to me), this would signals to external actors that
consensus rules can be changed by exercising the right pressure on the
right companies - and we're literally talking of a dozen mining pools and a
dozen major paiement processors and exchanges, spread in only a few
jurisdictions. This would cast doubt on the entire ability of
cryptocurrencies to remain decentralised and act as censorship-resistant
medium of exchange and inflation-resistant store of value. Bitcoin's sole
comparative advantage over centralised systems would vanish.

Even if this fork wasn't a base block size doubling but a simple, symbolic
increase of one byte to base block size, it would still be a bad thing,
because it would show that consensus rules - and therefore the very nature
of the currency people use - can be changed by external actors. To me and
to many other people, this debate isn't about block size anymore: it's
about the survivability of Bitcoin as a decentralised system. The Bitcoin
community should be as amorphous and resistant to change as possible - even
to more technically sound changes like Segwit, and even when these changes
come from competent devs with a solid track record of defending
decentralisation and privacy.

Just because only a few thousands or dozens of thousands of early users and
cypherpunks out of a dozen million of users disagree with this fork doesn't
mean we can be ignored: Bitcoin rose to its current popularity (and value)
because we invested our time, our hopes and our money in it, and millions
of politically unresponsive BitPay or Coinbase customers will not make up
for our absence on a centralised chain.

Claiming that Segwit2X has consensus with the now standard line "those who
oppose it are only a few thousands, while NYA signatories have millions of
customers" is akin to the NSA claiming that a majority of citizens endorses
surveillance, "because only a few thousands nerds care about it". Claiming
the silence of a majority of stakeholders as a tacit endorsement of some
policy is a dangerous (and I would add immoral) thing to do, and is what
has led to the creation of the centralised institutions that Bitcoin aims
at replacing.

Bitcoin is a formidable opportunity to bring greater monetary, economic and
political freedom to all humans, and the single best hope of freedom-loving
persons in this otherwise authoritarian and freedom-hating century.
Regardless of whatever understanding or sympathy we may have for you and
other NYA signatories, we who care about those things can not accept
cooptation by companies who effectively are centralised points of failure
at the mercy of governments.

If I could sum up my position (and the position of many users preoccupied
with decentralisation), it would be: "let us scale wisely, without making
short-term compromises that would weaken Bitcoin's unique features". Merely
increasing base block size as soon as we lack space would be akin to
kicking the can down the road to serfdom. And changing consensus rules at a
whim - or worse, engaging in a 51% attack to coerce the community into
following the new rules - would get us there in no time.

And to respond to one of your points, Mike, wishing for both chains to
survive is certainly not about "pride": it's about giving a durable,
decentralised consensus system to the world, a system that can't be
coopted, coerced or censored.

Mike, if you have any question or wish to continue this chat privately feel
free to respond directly to this email. I feel that the differences between
our respective camps are born out of cultural differences and absurd
misunderstandings, and magnified by our good ol' tribal instincts; there is
no reason why we should go through a messy divorce when we all agree on
making Bitcoin the world's sole currency, used for both small purchases and
storing large amount of values. This is Bitcoin's destiny, and our
squabbles are petty in comparison.

Cheers.
Hubert
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