Nice summary, @MiaZmy , it was nice reading your summary, I think I see the reason why the author proposed private transactions, the reason was to help protect transactions from being attacked. To help a future reader to appreciate this topic, I think I have to define what private transactions means in this context. A private transaction is a special transaction that can be sent directly to miners, bypassing the public mempool by doing so, such transactions remain private (i.e., only present in the target miner’s mempool) until they are posted by the target miner, and cannot be monitored by others. As a result, attackers cannot see these transactions in their mempool, thus thwarting the attacks. I further noticed in this paper that 2.6% private transactions senders earned more than ten ETH as profits via MEV Bots. Attackers have already utilized private transactions to launch attacks, in these attacks, the attackers paid a large amount to the miner as a bribe to get their transactions executed. According to the evaluation, the miner earned as high as 700 ETH for mining a single private transaction. This can lead to serious consensus security issues, such as the undercutting attacks. I think private transactions are not always private. Why? This is because the author observed that by running two Ethereum nodes in two continents for nine days, shows 4.3% private transactions in our mempool, which means that they are actually not private. I think users should proceed with caution when sending private transactions.
Finally, there is private transaction leakage at around 4.3% percentage. The leaked private transactions against their intentions and may harm the profits of their users.