Let’s go back to the hash war. For most people, the hash war is the killer weapon that has never been deployed, therefore a lot of articles and predictions are erroneous. BTC.TOP is the only one that had experience in participating in a hash war of scale and any article that diverges from the discussion from this article (including views from CSW) are likely to be wrong.
We all know the 51% attack:
Attacker use more hashrate, mine blocks on the ‘attacker chain’ which is longer than the original chain
The ‘attacker chain’ will then be broadcasted to the entire network and the nodes will follow the rules: adopt the longer ‘attacker chain’ and abandon the original chain
The figure below shows how the ‘’attacker chain’’ will be accepted by the nodes as the main chain.
PS: to be accurate, the ‘longer’ chain here means the chain that has more ‘accumulated difficulty’, for example, a node would accept 2 blocks that have a difficulty of 10 and abandon 3 blocks that have a difficulty of 5 as 10+10=20>15=5+5+5. For convenient explanations, the rest would assume the the difficulty level is the same for every block.
Through a 51% attack, it can achieve all sorts of goals, for example:
When Tx1 (transaction 1) is confirmed, cancel Tx1, validate a conflicted Tx2 (transaction 2).
For instance when Alice use Tx1 to send 1 BTC to Bob and in exchange gets 100 LTC from Bob. When Alice received the 100 LTC from Bob, she can use a Tx2 where you used to send 1 BTC to herself, switch it with Tx1 and retrieve back the 1 BTC sent to Bob.
Using the blocks that mine by yourself (red blocks) to orphan the blocks mine by other miners (blue blocks), it would result in other miners to lose their mining rewards.
On top of the 51% attack, one can start “51% empty block attack”: the attacker would only mine the empty blocks (not including any transactions), refusing (orphaning) all the normal blocks mined by other miners to make the chain malfunctioning and no one could trade on this chain anymore.
Moreover, due to the orphaning of the blocks, the miners will stop mining for getting no rewards. Eventually, the chain will die.