Bitcoin Forum

Anyone notice how close deepbit is to going 51%?  :(

All right, you made the thread, I don't think I fully understand, please explain why DeepBit taking the 51% could or will mess things up?   Will they have somehow more so control at that 51% over all of mining somehow?  Aliens?  I really don't know.

so what?

One of the touted weaknesses of Bitcoin is having a single entity in control of greater than 50% of the network.

It enables the possibility of double-spends.

For god's sake man, the thread RIGHT BELOW this one is about the same thing,

http://forum.bitcoin.org/index.php?topic=26630.0

So I guess I will repeat myself too:

"For the thousandth time, having 50% doesn't really help your attack chances all that much compared to having 49%. And even if you do have that much, the worst an attacker can do is double spend their own coins. No one can take your bitcoins or anything (at least, not the ones with many confirmations).

The best attack a pool with >50% could do is begin going backward in the block chain to rewrite it. During that time, no one in the pool would be getting paid, so people would be like, WTF. The network hash rate would drop by half so more people would be like WTF. Sooner or later the plot would be revealed and people would switch pools. No big deal. End of story.

On top of that, the pool owner probably has a heavy investment in bitcoins. If he screws with bitcoins he is just hurting his investment. Who would do that? He could probably make many, many times more continuing to run his pool correctly then he could get from a few hours of double spends followed by a crash.

The only real effect a >50% attack can have is mucking up bitcoin. And it only lasts as long as the 50% remains in control of an attacker. A pool isn't going to have that for long."

We need BTCGuild backkkk~~~

Indeed I did make a thread, though I did not notice the security breach thread or else I would not have.  I assume you don't need the lengthy security explanation Hero Member.

Moderators feel free to kill the thread.

The upshot is that there isn't any security threat at 51% that doesn't exist at 49%. In either case, you have to get a little lucky and make more blocks than the rest of the network over a short period of time. You can do this when your only got 40%. If you get really lucky, a single kid with a CPU can do it. There is nothing magical about 50% or 51%.

Thanks for the education, damienblack.  All that you've said makes sense for a group of miners who in the end are motivated by their own selfish interests (nothing wrong with that). But what if bitcoin were attacked by an adversary with unlimited resources (say the western banking establishment) and sustained the attack for an extended period?

Thanks. I'll join deepbit with my 1Ghs

I think if a bank or large organization wanted to squash bitcoin it would be far easier and cheaper for them to disrupt mtgox.  Anyone with enough coins can completely sabotage the price without even having to sell many coins.  Keep that up long enough and bitcoin will falter.  No need to attack the protocol, simply put huge stacks up and work the market down.

That would kill it. If an outside attacker had a network bigger than ours, and the intent to destroy it, our network would not be able to run while under attack. This is why we "pay" miners so much, they secure the network. But, to put things in perspective, our network is many times larger then the top 500 supercomputers in the world combined. It would be very hard to mount that attack. If our network power keeps going up, in six months I would say it is downright impossible.

http://trololololololololololo.com/

Saying there is no difference between 49% and 51% is somewhat misleading. At 49% you might get lucky and have a double spend accepted sometimes, but at 51% you will absolutely always be able to get a transaction rewritten.

Regardless, even if 50% wasn't specially, which I think it is. When do you think is the right time to talk about about this? When one kid turns on a CPU since he could get lucky enough? Or when I have 90%?

I don't mine, but deepbit must be freaking awesome for fully half of the network power to not care about the chance that feds show up with weapons to deepbit's house. This wouldn't permanently damage damage Bitcoin, but it would be annoying and it would damage reputation.

We're talking about a stochastic process, it's all about probabilities, there is specific information in the original Bitcoin paper by Satoshi.

Really? I'm suppose to mine somewhere else on the off chance that the feds show up with weapons, and the programing skills to rewrite the system to start generating blocks backwards. And so what if they do? Deepbit stops making me money or showing up in the charts while it tries to slowly outrun the rest of the network (but with only a 1% advantage good luck getting very far). That is about when I'll switch.

The feds have no more motivation to do that at the moment then the pool operator himself. It is a silly scenario that actually doesn't really have dire consequences.

And you could only "absolutely get a transaction rewritten" given enough time, which, with only a 1% advantage would take a long, long time to play out.

I agree the consequences are not dire and I'm not saying it's wrong or dangerous to use deepbit. I'm just saying as a non miner they all seem roughly the same, but since one has so much market share it must really be good in some way.

I was going to rebut the "takes a long time" point, but I just realized the 50% is a bit less magical than I thought. Sometimes it'll be quick (coming back from 2 confirms), but those are roughly the same times it would have been possible to double spend with 49% anyway.

interestingly, while difficulty jumped only slightly, the deepbit's hashrate jumped very significantly.

it seems like many miners are migrating to deepbit, probably for more stable payouts?

or other pools are very unlucky and/or unstable?

btcguild is under ddos.

In the light of the GHash-pool issue, let's get this thread from 2011 here back.

I guess the market share hasn't worked out too well for Deepbit...:

https://blockchain.info/de/pools

The point of bringing this thread back is ...?