According to a previous report by Zombit, a user paid 83.65 BTC (equivalent to 3.1 million USD) as a transaction fee in order to transfer 55.77 BTC (equivalent to 2.1 million USD), setting a new record for the highest transaction fee in USD for a single Bitcoin transaction, surpassing the previous record of 500,000 USD by six times. Additionally, data from the Bitcoin browser Mempool shows that the fee paid by this user was approximately 120,000 times higher than the normal value at that time.
Victim responds
Reasons for hacker attacks and high fees
Originally, the community thought that the protagonist of this incident might be a result of a system error, similar to the previous Paxos case. However, a user named Hackers_paid_83.5BTC_fee_with_my_money (@83_5BTC) claimed to be the protagonist of the event on the platform and used the principle of “asymmetric encryption” to prove that he was indeed the owner of the wallet.
@83_5BTC stated that he had intended to send the Bitcoin to a new cold wallet, but the Bitcoin was immediately transferred by a third party upon arrival. The attacker successfully stole nearly 56 BTC and also paid a fee of 83.7 BTC. As a result, the victim’s total loss was 139.42495946 BTC.
Bitcoin developer mononaut speculated that the wallet may have been compromised due to insufficient entropy. If the randomness used in generating the private key for the wallet is not good enough, such as using a simple human memory pattern (brain wallet), insufficiently random number generation methods, or using insecure pseudo-random number generators (PRNG), the private key could be calculated by others, allowing hackers to control the wallet and steal the encrypted currency inside.
As for why the hacker would pay such a large fee, mononaut believes that the hacker may have set up robots to monitor a large number of “low wallets” and automatically empty them once Bitcoin is transferred in. In order to prevent competitors (or victims) from attempting to broadcast replacement transactions, the hacker configured the robots with extremely high fees.
Coincidentally, the transaction fee for this large transaction was 83.65497568 BTC, exactly 60% of the total wallet assets (139.42495946 BTC). This seems to imply that the attacker configured the robot with the setting of “paying 60% of the total Bitcoin as a fee”.
As of now, it is unclear which company’s wallet the victim used, and it is also unknown whether the Ant Pool that mined the block is willing to return the 83.65 BTC fee.
However, the community is currently waiting for @83_5BTC to provide further response, as if the hacker truly has the ability to control the wallet and transfer assets, it means that @83_5BTC may also be the hacker, not the victim.