A virtual currency Bitcoin Gold has been hijacked by "51% attack" and the exchange incurs a large loss
"Bitcoin Gold (Bitcoin Gold: BTG)" which is one of the alto coins born in the hard fork from the virtual currency Bitcoin (bit coin)51% AttackIn response to the attack called the virtual currency exchanges incurred a massive loss occurred.
Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions
"51% attack" is that malicious virtual currency minor individuals and groups dominate over 50% of the network's total mining speed, hijacking the transaction and enabling unlawful transactions. This is to exploit the mechanism that transactions in the longest chain chain are recognized as correct transactions, so that malicious attackers mined at speeds that exceed those of other worldwide miners , Letting the attacker recognize that illegal transactions are "correct".
51% Attack - Bit Coin Glossary - Commentary on Bit Coin | Bitcoin Japanese Information Site
When a 51% attack is done, the mechanism that the block chain guarantees the transaction contents will not function, and one currency will be present twice. In other words, double payment becomes possible from 1 unit currency, so 51% attack is "Double Spend Attack"It is an attack that is executed in pairs. Normally, it is very costly to prepare an environment that can handle about more than half the transactions of the entire network, but after the execution the currency amount doubles to obtain the benefit of exceeding the cost It is said that it can do.
The BTG that was attacked this time is a virtual currency which was hard fork (incompatible division) from bit coin in October 2017. Edward Iskra, Bitcoin Gold spokesperson, notifies you that you are under attackentryOn May 18, 2018, encouraging vigilance against BTG being stolen from exchanges.
Double Spend Attack on Exchanges - Announcements and Site Feedback - The Bitcoin Gold Community Forum
An attacker who took over the network's processing remitted the same currency to Wallet under his control while depositing the BTG at the exchange. At this time, in the normal state, only the first transaction is made legitimate according to the mechanism of the block chain, but the content of the transaction is twisted because the network is contained under the attacker's control, and both The trading contents of each will exist as legitimate ones respectively. As a result, the attacker withdrew the coin immediately at the exchanges. After that, we succeeded in sending the original coins to another wallet by returning the transaction to the initial state.
Related to this attackBTG address, It is clear that 388,200 BTG or more coins were sent after May 16. Assuming that all of this coin was brought by an attack, it means that the attacker actually earned $ 18.6 million (about 2 billion yen) of funds.
BTG developers are advising exchanges to avoid problems by increasing the number of necessary transaction confirmations. According to the data in the block chain, since the attacker succeeds in rewinding the transaction of 22 blocks, it advises that at least the number of blocks necessary for confirmation is set to 50 or more.