Bitcoin miner concentration just exposed a gap in Bitcoin’s “six confirmations” rule

A recent two-block reorganization on March 23rd, involving Foundry, AntPool, and ViaBTC, exposed a vulnerability in Bitcoin's traditional six-confirmation finality heuristic. This rule, derived from Satoshi Nakamoto's whitepaper, assumes an attacker controls about 10% of the network's hashpower, yielding a low reversal risk (0.02%). However, with Foundry holding around 31% and the top three pools controlling 60% of the hash rate, the reversal risk under the same model climbs significantly, nearing 18.9% against a 32.2% attacker share. This concentration is exacerbated by deteriorating mining economics, which incentivize smaller miners to join larger pools. While exchanges already use lower confirmation thresholds (e.g., Coinbase uses two), the gap between the cultural standard of six for large settlements and the actual risk profile under current conditions is widening. The event suggests that the six-confirmation rule is becoming an unqualified standard, necessitating dynamic confirmation tiers based on transaction value and observable pool concentration.

(Source：CryptoSlate)