BTC Total GHash/Sec almost 15000. 51% Attack?

[Kumala]

Did anyone notice? I just looked on allchains.info.   BTC hashing power shows 15000 GHash, a few days ago it was somewhere around 8000. Who just joined the game? I hope this is not one single entity otherwise we have to fear a 51% attack (though not sure where the economical feasability of that is, adding 8000 GHashes is something like 10000 Radeon 6990 cards plus the power costs). What happens if that entity disappears again soon? We all remember how that went with Namecoin some months ago, a vicious cycle starts.

[elggawf]

I was confused about this a while back, but here's the skinny on the hashrate guesses.

Yes, they're guesses. I believe they're a product of difficulty and how fast the last couple of blocks have come in. Apparently the network just got pretty lucky a little while ago, and there's also talk of the difficulty drop meaning a few miners are coming back on that were previously turned off. But it's probably just more likely the network got insanely lucky for a short period.

But if you look now, the rates are back down where they're supposed to be. So no, probably nothing fishy going on.

Also, the 51% attacks, as I understand them, are more effective if you pick a spot to fork from, and if you do that with your 101% of the current hashrate, the Bitcoin-proper network won't see it until you announce those blocks onto the main network. So it's not just a case of: "Giant increase in hashrate? We're under attack!"

[Kumala]

Looks like your right. The hashes are already going down again. I tend to watch this carefully as running an exchange bears certain risks.

[MaxSan]

This is correct only based on previous time to solve blocks. It wont be reliable until maybe 100 blocks are produced.

[molecular]

http://bitcoin.sipa.be gives a much saner and less jiggly view of the hasrate, there's different averaging periods being used in the graphs.

[ElectricMucus]

Lots of miners play the on/off game right now, each time the difficulty drops they come back and switch off again when the price goes down.

[elggawf]

Lots of miners play the on/off game right now, each time the difficulty drops they come back and switch off again when the price goes down.

The hash rate data doesn't support that hypothesis, IMHO. It's a logical conclusion to draw, but when you look at the hashrate data (see the charts linked above) it doesn't look like any substantial amount of miners has come online since the difficulty drop. We're actually right now (according to BitcoinCharts) still below the 6/hour target.

[ElectricMucus]

Lots of miners play the on/off game right now, each time the difficulty drops they come back and switch off again when the price goes down.

The hash rate data doesn't support that hypothesis, IMHO. It's a logical conclusion to draw, but when you look at the hashrate data (see the charts linked above) it doesn't look like any substantial amount of miners has come online since the difficulty drop. We're actually right now (according to BitcoinCharts) still below the 6/hour target.

It looked like that on this graph the moment I posted it.


Onset was before the actual drop, so my hypothesis was/is that they wait till the estimate is sufficiently reliable.