Topic: New method of 51% attack? - page 2. (Read 3961 times)

Don't you mean 102%? Also I don't know if you guys remember but this actually was possible for ASICMINER with their first line of products. They, for a short while, actually achieved 51%+ and could have ruined this experiment for us all or at least damaged the functionalities and exchange rate more than what Mt. Gox has done, on many occasions.

Bitcoin is so resilient it actually survived a hard long fork on version "I think" 0.6?0.8?.

Now guys look at another attack vertex. How about not attaining such hash power but highjack just a couple of big pools at the same time. Infiltrate and sleep and pick the worse moment, say when the operators are sleep. And fork this thing real hard or block ALL transactions but just mining empties. Granted the miner will switch but it just needs a little time and a couple of discrediting hate articles and boom. Price down hard!

To mine two chains you need double the power, so in this scenario the “51%” would actually be 25.5% and 25.5%.

can u please explain it little bit more

i dont know if this has been discussed or not but 1 thing for sure is that a bad guy will always find another way to do bad things as usual, its like coded inside his body

Haha, you made me realize the title of this thread sounded way too general. I'm talking about a specific type of 51% attack. 

No, not ever discussed at all.

I don't know if any one entity has the power to do that to be honest.
Interesting thought though! 

Repeated Chain Replacement Attack

One of the most disruptive 51% attacks would be a DDOS attack where the miner with the majority of the hashing power only mines on its own blocks and doesn't mine any transactions.

Possibly even more disruptive, though, would be a miner who continually keeps 2 chains going at the same time with some double spends on each chain. The miner works on chain A and chain B, and lets the network keep building as well. But whenever everyone else in the network is building on chain A, the malicious miner will mine on chain B to make it catch up (and vice versa). The miner could even purposefully spread double spends between the two chains. Even transaction malleability could be utilized between the two chains, putting essentially the same transaction on the two chains, but with different hashes. This would make the network very unreliable and hard to use.

(I first thought that this might even lead to CPU exhaustion of the nodes, but I realized that nodes don't re-check all the scripts every time the connect a new tip to the head of the chain, so this probably wouldn't lead to any such attacks.)

Has this attack vector been discussed at all? I can't find any mention of it. I'm not saying I think this is likely to happen in the near future or anything, just that it would be fairly devastating if it did.

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Explained through ascii block chains:

Suppose the chain is at this state (each * is a block)

-- * -- * -- * -- *

Now the miner with 51% decides he is going to launch this attack. Let's say that the network is the first one to solve a block:

-- * -- * -- * -- *
                         \ -- *

Now the miner solves blocks on a chain opposite to it until the chain takes over. This might take a few blocks because the network is still working on the main chain.

                         / -- * -- * -- * -- *
-- * -- * -- * -- *
                         \ -- * -- * -- *

At which point the network switches to the top chain and the miner switches to mining on the bottom chain. The same thing happens, the miner's chain will eventually overtake the network chain (which is now the top chain), but it might take a few blocks.

                         / -- * -- * -- * -- * -- * -- *
-- * -- * -- * -- *
                         \ -- * -- * -- * -- * -- * -- * -- *

Now everyone else in the network switches back to the bottom chain, and the miner switches to mining the top chain. In each chain overhaul, the miner can include some double spends if they see any, and can alter transactions slightly through their malleable parts to make them have different TXIDs. The miner can keep doing this until the fork becomes ridiculously long and the data between the two chains is completely incompatible.