
On the growing risk of the 51% attack against BCash - yourrng
https://notehub.org/nz8d0
======
toomim
A 51% attack only allows you to (1) censor transactions for a short time, and
(2) double-spend. The first part is a mild nuisance. The second one can be
retaliated against off-chain, which puts the attacker (who must be a large
entity) at great risk in the real world.

~~~
VMG
> The second one can be retaliated against off-chain.

What do you mean?

~~~
gizmo686
If you do a double spend attack of any significance, the other party will
notice. Unless you are doing something completely anonymous, the other party
will also know who you are and be able to pursue other remedies (eg. sue you
for fraud).

~~~
tree_of_item
How could you possibly sue someone for double spending on a blockchain? I
don't get it, isn't the point of this blockchain stuff to be the wild west?
What is the grounds for a lawsuit? Why would a 51% attack be illegal? "Code is
law", right?

~~~
Sir_Substance
>I don't get it, isn't the point of this blockchain stuff to be the wild west?

I guarantee you no judge in the world is going to accept that interpretation.

>"Code is law", right?

From a legal perspective, obviously not, and given how well accepted the
etherium hard fork was in the wake of the DOA smart contract being exploited,
you can be pretty sure that a large percentage of the crypto-user population
doesn't think so either.

~~~
cies
Cardano is speaking out in favour of "code is law". Not sure what they do when
faced with an actual catastrophy. There are others also taking this stance to
some extend.

Anyway, Cardano is cool (Haskell, PoS, lots of papers published)

------
em3rgent0rdr
tl;dr: younger coins have fewer miners, so they are more susceptible to 51%
attack. In particular BCash has same hash function as BTC, so those BTC miners
could easily switch into mining BCash, and so is even more at risk.

~~~
oh_sigh
It would incur a huge opportunity cost for them to switch over, especially
because they would tank bcash by doing it.

~~~
em3rgent0rdr
Yes it would. This article is surprisingly ignorant of past discussion of the
%51 attack.

~~~
moduspol
It also fails to account for the possibility that Bitcoin Cash becomes more
valuable, and then Bitcoin is the "vulnerable" chain.

It also doesn't mention the name of the author, and the HN user who posted
this was created two hours ago.

HNers should understand there is a huge political divide in the Bitcoin
community right now on this very subject. Anonymous write-ups of known attack
vectors framed as genuine warnings are nothing more than unsubstantiated fear,
uncertainty, and doubt.

------
JepZ
When the BTC-BCH split happend I didn't really understand what everybody was
talking about transaction fees. So after BTC continued to rise the past months
and we have transaction fees >20$ I understand what was discussed earlier this
year.

I just wonder why the core devs were against increasing the blocksize. Yes, it
would not have been a solution for the next 20 years, but at least it would
have left the fees at a place where BTC was still suitable for the everyday
use until other solutions could be established.

~~~
fizzbuzzbazz3
There are many technical reasons, but I'll respond differently.

Bitcoin is not a business-coin. Bitcoin is an idea-coin. It was never about
the price, the price is just a side-effect. For many early adopters and
developers, Bitcoin is about changing the world. Not in a marketing bullshit-
world, but in a real way. We really believe that the world would be a better
place if we've put a stop to government and banks monopoly on controlling the
money. You may disagree, and it's fine. We believe in it, and we want to have
the most secure, uncensorable and attack-resistant value transferring network.
If it takes $30 to pay to transfer on such network, so be it. Increasing the
block size compromises on that property, so we are not willing to do it, even
though it's painful for everyone. We will wait. We have credit cards, we
PayPal, and we can use altcoins before we get there. The price will rise and
fall, users will come and go. We held at $1, we held at $10, we held at $20k,
and we will hold at $10 again if it's required. We will get our layer 2
solution and get both our uncensorable, government-resistant network and
instant cheap micropayments. That's why most of us dumped BCH coins without
thinking twice.

What most other coins are (not all!) is a business-coin. They are mostly
pointless. Ethereum could be really a centralized smart-contracts platform run
by Google or Amazon, and noone would care much. Actually, I believe that's how
ETH is going to end. I believe Amazon engineers are working on it already.
Because who cares about centralization or censorship resistance, if the main
use case is breading virtual cats? No government will be interested in
censoring that.

What BCash is, is a scam coin. It's all about ASICBOOST and Roger Ver's hurt
pride. He would like to be a pope of Bitcoin, but noone really cares about
him. Except for a talent for scamming people for his own gain, he is noone.

~~~
vongesell
I couldn't agree more. I'll add, if you are interested in making money there
are plenty of coin's, including BCash, to spend your time with. Go for it. But
if you are interested in something beyond speculation, it's pretty hard to
ignore the shady reputations and ecosystem of many of the most valuable
blockchains. Dash written and rewritten to centralize everything to Evan.
Ripple is basically the first ICO with all token being issued in the same
manner. It's pretty surprising these issues don't matter to anyone. The only
outlier really is Etherium. I think there should be both centralized and
decentralized systems and Etherium fits the former well and with the least
amount of scammyness in it's foundation.

~~~
clarents
While I'd agree that Ethereum was not created with an intent of scammyness, I
wouldn't single it out as an outlier for good behavior. The dream of Ethereum
was "code as law," yet key players have demonstrated the ability and
willingness to implement hard forks in order to undo unpopular outcomes of
valid Solidity code. So while I don't believe Ethereum was created with a
scammy intent, I think it is certainly too premature for public release, and
attempts to "fix" issues caused by this immaturity has let to some scammy
behavior.

------
ringaroundthetx
The was a long winded explanation of a 51% attack lol.

Was the author just talking about hashrate switching? Any solutions for
exchanges or merchants such as just increasing the confirmations required?

Any interest in bitcoin cash changing it's algorithm?

~~~
milcron
> Any interest in bitcoin cash changing it's algorithm?

I doubt it. One of the reasons BCH hardforked was so large mining pools could
continue to take advantage of Asicboost, a patented approach to Bitcoin
hashing that provides a 20-30% speedup.

Asicboost is essentially taking advantage of a flaw in the original Bitcoin
algorithm which leads to slightly predictable hashes. Segwit fixed this
problem, nullifying their patented advantage.

All of the vocal BCH supporters are involved with large sha256 mining pools. I
think it's very unlikely that they'll elect to change algorthms.

------
bishopknight
Not happening. ANT Pool has a huge investment in Bitcoin Cash and would swoop
in with mining power to protect their investment.

~~~
yourrng
Please re-read the post, because you don't understand.

The 51% attack is carried in secret. Noone has any way to know if it is
happening until the longer chain is published. And after that, it's too late
already. Someone could try to catch up with (not anymore secret) longest
chain, but the damage has been done - the state of the network has already
changed. Actually switching it back is only adding salt to the wound. Noone
would trust that coin again anyway, and it is worthless to try to rescue it.

AntPool is busy mining Bitcoin, because it pays better:

[https://blockchain.info/pools](https://blockchain.info/pools)

so it can't constantly police BCash chain by over-provisioning it.

------
deftnerd
I can't take any criticisms against Bitcoin Cash seriously when the authors
knowingly refer to it as BCash. It's not just a shortening of the name, it's
part of a concerted effort by detractors to distance the chain from the
Bitcoin legacy.

Any author that purposefully uses the term BCash is, on the face, incapable of
being objective because they're advertising that they're detractors already.

The Bitcoin Core (no on-chain scaling at any cost!) crowd _asked_ the on-chain
scaling fans to "fork off and leave". Now that the coin is doing very well in
terms of market value and especially in growing merchant adoption, they're
desperate to push the narrative that it's a scam or dangerous or can't be
taken seriously. They know that if they can't destroy Bitcoin Cash now, it has
a reasonable chance of eventually overtaking the legacy Bitcoin network in
every important respect.

~~~
MintPattern
It’s called bcash in hopes that too many newbies won’t go deposit bitcoin into
a “bitcoin cash” address and sadly lose it all.

~~~
toomim
Again, this is a myth spread by people trying to tarnish Bitcoin Cash's image.

The truth is that the money can't be lost. If you have the Bitcoin Cash
private keys for the deposit address, you have the Bitcoin Core private keys
on the Core chain. All that happens is that someone accidentally receives
Bitcoin Core instead of Cash.

~~~
MintPattern
A lot of newbies put everything on an online exchange and don't bother with
handling private keys. I haven't found a single exchange yet where you control
the private keys. The public keys on exchanges I've seen are different for
Bitcoin Cash and Bitcoin. Also, can you imagine the end result of paying for a
good or service that accepts Bitcoin with Bcash?

------
jVinc
I like the math and theory on this. But really why would someone who's making
millions on the status quo risk tanking the market for a one time gain? Seems
unlikely.

~~~
yourrng
You don't have to risk anything. If the trend continues, at some point one
would be able to rent the mining power required.

On top of it, if you are a small miner, and you can't afford capital
investments required to keep up with latest mining hardware, while loosing
market share, you can use your soon-osolete hardware to make a one last buck.
A big buck this time.

------
stale2002
OK, this is describing a 51% attack.

And who would engage in this 51% attack? The miners?

The miners are one of the biggest groups that SUPPORT Bitcoin Cash, so I find
it unlikely that they would spend millions attacking it.

Anyway. It matters not. The people that want Bitcoin to be a settlement layer
are free to spend 50$ per transaction to use Bitcoin, and those of us who want
to use it as an actual peer to peer electronic currency will use Bitcoin Cash.

Everyone wins. It doesn't really matter what is the "real" Bitcoin.

~~~
mplewis
Anyone who's mining Bitcoin could switch to Bitcoin Cash and work to perform a
51% attack.

> BCash shares hashing algorithm with Bitcoin. That means any hashing power on
> the Bitcoin network can work on BCash network. And there is typically 10
> times more miners mining on BTC, than on BCH because of the difference in
> the price and minning fees.

~~~
stale2002
And which miner SPECIFICALLY would do that? There are only like 7 major mining
pools. Which of those 7 do you think would do an attack?

The miners were the ones who helped create Bitcoin Cash. Why would they attack
it?

The miners are the largest supporters of big blocks, so it make no sense that
they would attack the thing that they helped launch.

Also, people don't seem to realize that it is already possible to do a ~20
percent selfish mining attack. And yet we don't see THAT happening...

These attacks aren't realistic in practice because it would be immediately
obvious that something is happening, and the miners would lose all their money
as Bitcoin crashes.

~~~
yourrng
Let me count some scenarios:

* a miner losing its share in the competitive game could make a one last money grab before its hardware is obsolete

* BCash backing miners losing confidence in success of BCH could just damage the whole space, for revenge or and profit

* complete outsider like an angry government could try to disrupt the space to ban all crypto or at least heavily regulate it / buy some time

------
omarforgotpwd
Who is seriously going to try and execute a 51% attack? It would be so
incredibly expensive, you would have to keep spending more as people added
hash power to shut you out, and most importantly if your attack worked you
would instantly undermine the security of the blockchain making all the
currency you've stolen worthless!

------
lurr
> But I’ll try to explain everything technically and stay objective

You failed inside of 3 paragraphs.

~~~
moduspol
The headline used the term "BCash." It'd be tough to have an objective post by
someone about "BCore," too.

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ErikAugust
Is it possible it's already happened? I have no idea what the mining breakdown
looks like - but I'd imagine it's only a couple players mining BCH. I'd think
you could rewrite the chain at will pretty much.

~~~
VMG
We would see two chains forking of a shared block with a significant length
(~10). Unless you count Bitcoin Clashic[1], there's no proof of that

[http://bitcoinclashic.org/](http://bitcoinclashic.org/)

------
ubu7737
The spectrum is really marvelous. It's amazing to see how many different kinds
of people, with many different motivations, will waste their time on
speculative crypto-coins.

