About 25% attack ,Is that true ?

lizhi

Majority is notEnough: Bitcoin Mining is Vulnerable
ttay Eyal and Emin GÃ¼n Sirer
Department of Computer Science,Cornell University

Abstract. The Bitcoin cryptocurrencyrecords its transactions in a public log called the blockchain.
Its security rests critically on thedistributed protocol that maintains the blockchain, run by participants calledminers.
Conventional wisdom asserts that theprotocol is incentive-compatible and secure against colluding minority groups, i.e.,it incentivizes miners to follow the protocol as prescribed.
We show that the Bitcoin protocol is not incentive-compatible.
We present an attack with which colluding miners obtain a revenue larger than their fair share.
This attack can have significant consequences for Bitcoin: Rational miners will prefer to join the selfish miners, and the colluding group will increase in size until it becomes a majority.
At this point, the Bitcoin system ceases to be a decentralized currency.
Selfish mining is feasible for any group size of colluding miners.
We propose a practical modification to the Bitcoin protocol that protects against selfish mining pools that command less than 1/4 of the resources.
This threshold is lower than the wrongly assumed 1/2 bound, but better than the current reality where a group of any size can compromise the system.

Skull88

Selfish mining is already debunked, nothing to be worried about. ;)

wrapper

Not true, or likely. How can you be selfish and destroy the network? Also, it relies on a pool keeping back a completed block, which is unlikely to be possible consistently, due to the probability of someone else on the network finding the block.

The other problem with it is, the networks are being monitored more closely than the writers suspect, so the attack would be noticed.

Pretty much scare tactics, only actually viable as an attack by a large outside agency, not selfish miners. The alt currencies are dealing with real attacks, not just imagineering.

zerodrama

They don’t understand the difference between the txchain and the blockchain.

The blockchain is a record of protection work. The txchain is a record of sends and receives.