Antpool, the second-largest Bitcoin (BTC) mining pool, mined seven blocks in a row on May 17, raising security concerns. The seven-block sequence confirmed 20,686 transactions, rendering over 23 BTC, worth around $1.54 million, in revenue.
In particular, the event happened between block heights 843,898 and 843,904 and lasted one hour and 38 minutes. According to mempool. space data, Antpool collected 1.283 BTC in fees, plus 21.875 BTC from the block subsidy.
Block heights 843,898 to 843,904. Source: mempool.space / Finbold
Interestingly, Foundry USA, the largest Bitcoin mining pool, mined the previous block of this sequence and the two next blocks. This makes a sequence of 10 blocks mined by two companies, challenging the decentralization and security of the leading cryptocurrency.
The Public Pool account raised the security concern in a post on X.
Bitcoin mining pool centralization and security concerns
Essentially, the proof-of-work consensus mechanism Bitcoin uses establishes a round leader to add transactions to a block and broadcast this block to the network peers, who will add it to their ledger. The leader is the miner who finds the next valid block according to the hashrate each miner produces.
Bitcoin’s security premise lies in the idea that different entities that do not know each other will find different blocks. This prevents a malicious actor from spending the same coin twice or adding an invalid transaction to the blockchain.
Moreover, having multiple miners competing equally diminishes the chances of a “chain reorg.” The reorganization excludes blocks from the blockchain and could revert confirmed transactions—as if they never existed.
Bitcoin mining pools are considered a single entity despite having multiple miners working for them because the pool coordinator manages the contributed hashrate, adds transactions to blocks, broadcasts blocks to the network, and pays the contributing miners accordingly.
Who is Antpool?
Antpool is a Chinese company subsidiary of the world’s largest Bitcoin mining equipment producer, Bitmain. In November 2023, the company raised controversy in the Bitcoin community by arbitrarily refunding an 83 BTC fee.
Notably, the pool has mined 25.48% of all blocks in the last seven days. It loses only to Foundry USA, with 31.12% of the network’s hashrate—both with a 56.6% mining dominance. In October 2023, Antpool briefly challenged Foundry’s leadership for three days.
Bitcoin mining pools weekly ranking. Source: mempool.space / Finbold
In this context, a Bitcoin developer believes transactions should wait at least two hours before being considered secure. This is because the more subsequent blocks after the one carrying a transaction, the lower the chances of a chain reorg and the more probable a transaction is to reach finality.
Antpool’s recent seven-block sequence demonstrates that the developer’s concerns are real and should be considered.
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