Can't bitcoin simply require agreement from more than one author of a blockchain? For example do not allow the same entity to sign the blockchain for two consecutive blocks. This would require defining what constitutes a single entity though. How do we define it when talking about mining pools? Can't we have alliances of pools already have reached 51% long ago and colluded "as one strategy"?
It's Time For a Hard Bitcoin Fork
151–154 of 154 posts
Re: It's Time For a Hard Bitcoin Fork
#152Earlier quoted context omitted.
In other words, the stars would have to align in order for this to occur. I don't really know what GHash knows, but I can tell you that GHash's hashrate has dipped well below 50% only a day later, as it did when this happened before.
The stars would have to align for it to be genuinely a good idea. Which... well... stars align, sometimes. Moreover, people make mistakes and think stars have aligned. The threat here is that a single group has the capability to produce 51% of the hashes, possibly reliably (we can't know whether scaling back was deliberate or happenstance). It doesn't matter whether they are persistently using that capability.
Large contributors to the GHash pool pulled large amounts of resources out of the pool. GHash isn't a monolithic entity. Miners have to voluntarily commit their resources to GHash. It's not like a single individual can commandeer the entire mining army without fear of repercussion.
Re: It's Time For a Hard Bitcoin Fork
#153Earlier quoted context omitted.
I think I understand now. That would still be a bit of a tricky position because it isn't so much 51% when you commit the fraud that is important it is the period following the fraud. How detectable would such an action be? Wouldn't other systems be able look at the block and say "it's verified, but it don't look right to me"
You pretty. Much have to detect the fraud before/as it occurs - the dominant miner being silent for a while is a good indication they are building an alternate chain in private, for example. At least, that would be an indicator for a double-spend.
Not really. That happens regularly just because of luck.
Re: It's Time For a Hard Bitcoin Fork
#154I was under the impression that the mining percentage would give you the same percentage chance to cook the books. 51% means you are more likely to succeed than fail in an attempt. Much like buying 51 percent of lottery tickets gives you a slightly better than even chance of winning the big prize. in that respect, wouldn't 51% be only marginally different to 49%. Both would be a bit of a concern, but neither would be…
From the bitcoin wiki: An attacker that controls more than 50% of the network's computing power can, for the time that he is in control, exclude and modify the ordering of transactions. This allows him to: Reverse transactions that he sends while he's in control. This has the potential to double-spend transactions that previously had already been seen in the block chain. Prevent some or all transactions from gaining…
Wait. If the attacker did any of that while it was in control, then wouldn't it fail validation for every other bitcoin miner?
If they lose their 50% control then they generate invalid blocks. Particularly the part regarding the number of coins generated per block. That one will obviously be wrong.