

BTC mining pool just reached 50% global mining power - ikken
https://blockchain.info/pools?timespan=24hrs

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chicagomint
Why does this matter?

One of the most notorious threats to blockchain-powered networks is allowing a
malicious actor to obtain control over more than half of the network's
computing resources. This situation is commonly referred to as the elusive
"fifty-one percent attack." It is difficult, but not impossible to pull off
—[http://motherboard.vice.com/blog/bitcoins-fatal-flaw-was-
nea...](http://motherboard.vice.com/blog/bitcoins-fatal-flaw-was-nearly-
exposed) — the aggregation of this kind of hashing power. And it looks like
we've nearly made it there again, but there is a difference between a pool
getting > 50% of resources, and an "attack."

A successful attack using this method would allow the attacker to exclude, or
"orphan" any new blocks from the valid chain causing all newly-minted coins go
to the attacker. He may also execute a "double-spend" and reverse any of his
own transactions during the window of time that his sham blockchain is
considered authoritative by the network.

A successful 51% attack on Feathercoin — [http://www.coindesk.com/feathercoin-
hit-by-massive-attack/](http://www.coindesk.com/feathercoin-hit-by-massive-
attack/) — was stopped in its tracks by the network's natural uptick in
difficulty in response to an increase in network hash rate. The Feathercoin
attacker was likely executing a price pump in parallel to compromising the
network, which caused coin-switching pools to mine feathercoin and increase
the difficulty to a level that stopped the attack.

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sampson-san
Interesting data point, thanks! If all the compute power that together forms
the GHash pool were controlled by a single entity, this would be an issue.
Thankfully that's not the case.

~~~
ikken
Please see my comment above. For all practical purposes, GHash pool owner
controls the whole hashing power - he becomes the owner of each mined block
and can do whatever he want's with it without users' consent.

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nestlequ1k
What % of HN knows what this means? Maybe this should be a blog post instead
and explain what a "mining pool" is. Or what is the significance of one pool
taking over the market.

~~~
sampson-san
Anyone familiar with Bitcoin is likely aware of the 51% attack. A blog post is
hardly warranted, because this isn't significant. GHash.io does not control
all of that compute power. It is a metalayer that coordinates distinct and
unrelated compute resources controlled by (supposedly) 180,000 seperate
entities[0]. In order for a 50% attack to take place the vast majority (at
this point) would have to agree to attack, and that simply won't happen.

[0] GHash.io homepage

~~~
ikken
I don't think you're right. The mining machines are pointed towards Ghash pool
owner and he becomes the owner of the mined block - that's how he can
distribute the BTC to everyone who contributed. So in practice, he controls
the whole hashing power and can perform the attack without users' consent.

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hitchhiker999
as a long time proponent of BTC, this is the first time I'm truly worried. Not
that I think GH will do anything 'dodgy', just that it's _actually happened_
and that's not a good thing at all.

GH just did a great job, I think when other competitors step up and provide as
good a service - this will become a distant memory of the past - a blip on the
radar (I hope).. There'll be a handful of decent pools, thereby never letting
this happen again. (I hope again)

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white_eskimo
Bitcoin was supposed to be a decentralized system, not one with a centralized
benevolent authority. In GHash We Trust...

~~~
cLeEOGPw
Well, nobody is forcing anyone to participate in the pool. People can just
switch to other pools. But here again greed will win, because those who
participate in biggest pool can expect most reward.

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vayan
and how much of the "unknown" is owned by GHash ...

