Topic: SPV wallets AREN'T safe for the upcoming segwit2x attack (Read 534 times)

Bitcoin IS elitist in nature. If you are not validating your own transactions, you are not really using bitcoin, it's really that simple. If you are trusting someone else, then you can't call it trustless or permissionless, it's as trustless and permissionless as whoever you are trusting to wants it to be.

Sure, average joe is way better off using an SPV wallet than a bank account when it comes to sovereign money and privacy, but let's be real.


Anyone can fork the coin. Bitcoin Cash did it right. Bitcoin Gold will do it right. Segwit2x is NOT doing it right because they pretend to call it "BTC" in exchanges, and often times they hate the fact that an exchange will list both BTC and B2X, because they hate that their coin would be exposed having no economic backing behind bribed CEO's into supporting GarzikCoin. Let the market decide, then you will see the market doesn't want this shitcoin2x.

Again, Bitcoin is NOT CEO's gathering and deciding what Bitcoin is, the market will prove this right (and that is why they are scared of it).

Full control means having your own private keys, it doesn't necessarily mean a full node: you can have your keys offline...


Exactly this, Electrum won't follow anything, servers that provide Electrum services will.


Food for thought.

"Validity" is a matter of perspective and depends entirely on the choice of code you freely choose to run.  Those small number of people currently transacting with BCH aren't doing so to intentionally trade invalid tokens, for example.  They're doing it because they want to and feel sufficient incentive to do so.  As such, I don't think anyone is suggesting that the most-work chain can force a change of consensus that a supermajority of users opposed.  It's more a question of whether the supermajority of users:  

a) really is a supermajority, but we can't put the cart before the horse and assume that it is

and

b) whether or not these users' preferred chain would have sufficient transaction volume to be a greater incentive to the miners than the forked chain the miners are proposing.

My argument is essentially that users and miners are free to leave if they feel they have an economic case to do so, but those who want to remain on the original chain don't have to change a thing (with the possible exception they find themselves short of hashpower).  It's then down to the users and miners of the original chain to prove them wrong, because that's how a market works.  You can't just claim you have the superior software and try to prevent them from leaving.  You have to allow them to leave and then realise their mistake (assuming it does turn out to be a mistake).  After all, it's their hashpower they'll be wasting if their new chain doesn't have enough traffic to sustain it and make it financially viable.  One way or another, there will be a natural and organic alignment of incentives.  There could be a winning and losing chain, or both chains could survive resulting in a permanent split.  Either way, though, it'll be resolved and every participant can weigh up the pros and cons and decide for themselves what they want to do.

Admittedly, there is some risk for inexperienced SPV users if they aren't paying attention and a risk for any inexperienced users, full node or not, if they tried to move their 2x coins without taking adequate precautions.  But anyone who has access to their keys can ultimately choose which chain they want to follow.  

We should certainly recommend not transacting whilst all this upheaval is going on unless you know what you're doing.  

But still, the far larger risk is to all those countless users with their funds in the custody of a "trusted" third party like exchanges and webwallets.  They're the ones who need the loudest wake up call, since they're the ones truly using Bitcoin in a way that wasn't intended by design.  They are entirely at the whim of their custodians as to which chain(s) they may or may not have access to.

the risk is losing funds through replay attacks. for example, let's say you use blockchain.info -- you control those private keys. if you don't do anything (no transactions) after the fork, your coins are safe, so it's not unsafe to hold your coins there. the danger is in using blockchain.info's nodes to push/receive transactions. they may be following an invalid chain in which valid transactions can be replayed (and vice versa). that means that if you try to transact with legacy BTC, you could lose your B2X coins. If you try to transact with B2X, you could lose your BTC.

this could all be avoided if the segwit2x guys would just fork responsibly and add replay protection. the thing is, they need to harvest SPV wallet users (who blindly follow miners), otherwise their fork looks illegitimate with little to no economic activity.

So when we say "SPV wallets wont save you" and "SPV wallets are in danger", what do we actually mean?  That you can't hold Bitcoin in such wallets at all, or that they may be at risk if scenario x or y occurs, or that you risk losing Bitcoin if you do a transaction or can't claim/split the new coin?

I'm not likely to put big boy pants on and download 100GB, most people out there aren't going to be aware of this let alone attempt running full node.

You can set up your Electrum wallet to connect to whatever servers you want. Here is a list of of Electrum servers on the Bitcoin mainnet, along with which version most of them are running: https://uasf.saltylemon.org/electrum

When in doubt, don't do anything, and wait until some good tutorials are available for properly splitting coins and avoiding replay attacks. There is still time for BTC1 to add replay protection, and I hope they do. Otherwise SPV wallet users are indeed in danger.


The most-work chain is only part of the consensus mechanism. The whitepaper and cursory observation of the Bitcoin network confirm that validity is integral to the consensus process, and that incompatibility breaks consensus (split networks). That is to say, users (including miners) can leave the consensus anytime they want. But they cannot change the consensus reached by the prior network.

The reason that this is an issue is because SPV users don't enforce Bitcoin's rules. They could just as easily follow a chain with 84 million BTC, as long as transaction/output format is preserved.

heavily waiting for this one 

That sounds like an unfeasible expectation, to put it mildly.  By asking every participant to run a full node, all you would be doing is driving casual users away.  The option should be there for those who genuinely wish to run a non-mining node, but it shouldn't be some sort of elitist "you're not really one of us unless you meet our standards" kind of BS.  Also, way to relegate many of the smartphone users from the poorer parts of the world into the category of worthless passengers with "no skin in the game".  Your entitlement is showing. 

And again, whilst it tends to be the prevailing narrative on these boards that 2x is some sort of "attack", some would merely see it as a difference of opinion and wouldn't feel the need to "defend" Bitcoin like it was some sort of fragile infant with an autoimmune disease.  I'd like to think it's a little more resilient than that.  Think about this carefully:

What's the point in even *having* a consensus mechanism if you're too afraid to let it do its job? 

If you think it's better to put a gun to everyone's head and tell them exactly what to run, the consensus mechanism is wholly redundant.  You might as well close the source as well while you're at it.  No one can make any more forks then.  Would that make you happy?

The entire idea behind it is that you don't need trust the other network participants or "defend" the network from those you might disagree with.  Everyone runs what they want and there's no need for brigading.  The network will sort itself out.  Bitcoin doesn't require any populist uprisings to rally behind certain developers in order to function.  It doesn't need you to shelter it from a reality that isn't nearly as harsh as you make it out to be.  It's self-regulating for a reason.

Thats not true at all. As long as you are in control of your private keys (doesnt matter if they have been generated by a core wallet or by any other wallet)
you are fine and can decide for yourself which "chain you follow".
And additionally al ot of wallets provide both chains (e.g. electrum if im not mistaken).

Indeed, it seems like SPV clients might be vulnerable to this segwit2x attack

https://bitcoin.stackexchange.com/questions/60360/segwit2x-btc1-block-header-changes-wipeout-protection-for-spv-nodes

https://github.com/btc1/bitcoin/pull/46#issuecomment-312067571

So far segwit2x developers did everything to ensure that their hard fork will be as contentious as possible, and attack on SPV clients was exactly their goal.

Some time ago Electrum added a new feature called Multiple Chain Validation (MCV) which should allow Electrum clients to distinguish between different Bitcoin chains - https://electrum.org/bcc.txt

Also, I'd advice all SPV users to avoid doing any transactions after the hardfork and wait until the situation will resolve.

I think people has been lied to by telling them that they are in bitcoin when they don't even run full nodes. Any transaction that is not sent from a full node you control is not a real bitcoin transaction as far as im concerned, or might I say, a sovereign one.

If you are using SPV wallets, you aren't using Bitcoin. SPV wallets can be ok temporarily, but in times like these, you must show how much skin in the game you have, and defending against the segwit2x attack with a Bitcoin Core node is a must.

If you can't, then hold the private keys and don't transact until things are clear, or else you risk losing your coins.

And yes, ideally all of us should be mining, even if it's at a loss, but that's too hardcore for most people.

You can select what chain you will follow with Electrum Just use a server that follows your preferred chain.

I have my doubts whether a significant proportion of users would go to the effort.  It's difficult enough to convince many of them to use SPV over webwallets and exchanges, so they at least have control over their private keys.  Running a full node is also tricky in that not all users will have sufficient resources in terms of bandwidth.  There's a "path of least resistance" argument to be made.  Even if the average user did feel as strongly about this "attack" as you (and I'm not entirely convinced of that either), it's probable that people will choose convenience over politics.  

If people really do care, I suppose they'll find a way, but given what tends to be generally accepted about human nature, apathy and laziness should never be underestimated.



Then maybe stop relying on all these miners that you suddenly find yourself disagreeing with.  One could argue that if you really want to be in full and total control of your bitcoin destiny, you should grab yourself some mining gear and actually help build upon your preferred chain.

I dont't know what Electrum will do. The whole point of bitcoin is to not have to wait to what will someone else do for you.

There is a risk that SPV wallets will follow the longest chain or the one with the most hashrate.

Full control means a full node, end of story. Anything else is a compromise where you are trusting X to do Y: not good.

So the Electrum wallet will follow segwit2x?

Time to put your big boy pants and download a full node if you are into Bitcoin for real.

SPV will not save you in November. The segwit2x attack is a serious one, only full node users will be safe.

You have until November 17th to get a full node working if you want to be safe and control your own BTC:

https://coinsalad.com/2x/countdown

https://www.youtube.com/watch?v=lUNs6dA4cBI

Download Bitcoin Core today: https://bitcoin.org/en/wallets/desktop/windows/bitcoincore/