Q2: Cobra, moderator of Bitcoin.org, suggested this February that bitcoin should change its POW algorithm into the combination of POW+POS. And last Friday, he tweeted that you and Viabtc CEO Yang Haipo can easily start a 51% attack to bitcoin. But you responded that Cobra should read the whitepaper first before he wants to change it. And 51% attack will not destroy bitcoin. Could you further explain this considering 99% bitcoin users never actually read the whitepaper.
Jihan: Here is what the whitepaper says about attacking bitcoin—“We consider the scenario of an attacker trying to generate an alternate chain faster than the honest chain. Even if this is accomplished, it does not throw the system open to arbitrary changes, such as creating value out of thin air or taking money that never belonged to the attacker. Nodes are not going to accept an invalid transaction as payment, and honest nodes will never accept a block containing them. An attacker can only try to change one of his own transactions to take back money he recently spent.”
See? Even if attack happened, the whole system is not open to arbitrary changes. And the attacker is only able to change his own transactions and take back money he recently spent. Only part of users who are unaware of the attack and receive payment from the attacker will suffer a loss.
