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Ghash.io very close to 51% of bitcoin pool

bitcointalk.org

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Re: Ghash.io very close to 51% of bitcoin pool

#2
It might already be considering that there is a substantial proportion that is "unknown" mining power: https://blockchain.info/pools

On the other hand, the heuristics of blockchain.info do determine block ownership are not perfect either: https://bitcointalk.org/index.php?topic=123726.0;all

Re: Ghash.io very close to 51% of bitcoin pool

#4
post #2

It might already be considering that there is a substantial proportion that is "unknown" mining power: https://blockchain.info/pools On the other hand, the heuristics of blockchain.info do determine block ownership are not perfect either: https://bitcointalk.org/index.php?topic=123726.0;all

Can you explain what the threat is please?

Re: Ghash.io very close to 51% of bitcoin pool

#7
post #4
post #2

It might already be considering that there is a substantial proportion that is "unknown" mining power: https://blockchain.info/pools On the other hand, the heuristics of blockchain.info do determine block ownership are not perfect either: https://bitcointalk.org/index.php?topic=123726.0;all

Can you explain what the threat is please?

http://www.cryptocoinsnews.com/2014/01/09/warning-ghash-io-n...

---The attacker can----:

Reverse transactions that he sends while he’s in control

Prevent some or all transactions from gaining any confirmations

Prevent some or all other generators from getting any generations

Double spend Bitcoins

---The attacker cannot---:

Reverse other people’s transactions

Prevent transactions from being sent at all (they’ll show as 0/unconfirmed)

Change the number of coins generated per block

Create coins out of thin air

Send coins that never belonged to him

Re: Ghash.io very close to 51% of bitcoin pool

#9

Could someone with knowledge of Bitcoin explain what happens when a share of the pool hits 51%? Is this dangerous in some way? Edit: Thanks to those who took the time to explain. Very interesting.

Essentially, Ghash.io would be in control of the Bitcoin blockchain, allowing double spending of BTC and other nefarious deeds.

See https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_...

Edit: According to the Wiki linked, these attacks are also possible with <50% mining rate, although with lower probability of success. So this is a problem even if Ghash.io does not crack the 51%.

Re: Ghash.io very close to 51% of bitcoin pool

#10

Could someone with knowledge of Bitcoin explain what happens when a share of the pool hits 51%? Is this dangerous in some way? Edit: Thanks to those who took the time to explain. Very interesting.

My understanding is that if one entity controls 51% of the network, they can push arbitrary modifications into the block chain. In effect, they can do whatever they want.
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