新聞來源連結：
https://www.ccn.com/bitcoin-gold-hit-by-double-spend-attack-exchanges-lose-millions/
新聞本文：
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A malicious miner successfully executed a double spend attack on the Bitcoin
Gold network last week, making BTG at least the third altcoin to succumb to a
network attack during that timespan.
Bitcoin Gold director of communications Edward Iskra first warned users about
the attack on May 18, explaining that a malicious miner was using the exploit
to steal funds from cryptocurrency exchanges.
To execute the attack, the miner acquired at least 51 percent of the network’
s total hashpower, which provided them with temporary control of the
blockchain. Obtaining this much hashpower is incredibly expensive — even on
a smaller network like bitcoin gold — but it can be monetized by using it in
tandem with a double spend attack.
After gaining control of the network, the attacker began depositing BTG at
cryptocurrency exchanges while also attempting to send those same coins to a
wallet under their control. Ordinarily, the blockchain would resolve this by
including only the first transaction in the block, but the attacker was able
to reverse transactions since they had majority control of the network.
Consequently, they were able to deposit funds on exchanges and quickly
withdraw them again, after which they reversed the initial transaction so
that they could send the coins they had originally deposited to another
wallet.
bitcoin gold
Source: BTG Explorer
A bitcoin gold address implicated in the attack has received more than
388,200 BTG since May 16 (mostly from transactions it sent to itself).
Assuming all of those transactions were associated with the double spend
exploit, the attacker could have stolen as much as $18.6 million worth of
funds from exchanges.
The last transaction was sent on May 18, but the attacker could theoretically
attempt to resume it if they still have access to enough hashpower to gain
control of the blockchain.
Bitcoin gold’s developers advised exchanges to address the attack by
increasing the number of confirmations required before they credit deposits
to customer accounts. Blockchain data indicates that the attacker
successfully reversed transactions as far back as 22 blocks, leading
developers to advise raising confirmation requirements to 50 blocks.
At present, bitcoin gold ranks as the 26th-largest cryptocurrency, with a
circulating market cap of $827 million.
Bitcoin gold is at least the third cryptocurrency network hit with a major
attack in the past week alone.
As CCN reported, a miner manipulated two of privacy coin verge’s five
hashing algorithms to maliciously mine more than 35 million XVG — worth
~$1.75 million — in just a few hours. Previously, Japanese cryptocurrency
monacoin was hit by an apparent block withholding attack after a miner gained
as much as 57 percent of the network’s hashrate.
Featured Image from Shutterstock
評論：
沒想到有機會可以見證到51%算力攻擊