Error in Time-Locked Bitcoin Contracts Allows for Miner “Fee-Sniping”

Users have discovered an error in bitcoin “timelocked” contracts that could potentially allow miners to steal BTC from one another. 

Anonymous crypto engineer 0xb10c reported discovering more than one million “time-locked” transactions made between September 2019 and March 2020. In a post, 0xb10c detailed how these special bitcoin transactions were not being accurately enforced by the network. 

As opposed to normal transactions, time-locked transactions prevent recipient bitcoin from being accessed after sending. Users must wait for a specific number of blocks to be added to the network in ten-minute intervals before gaining control of their bitcoin. 

0xb10c claimed the errant time-locked transactions provided an attack vector for miners to steal transaction fees  from one another via “fee-sniping.” According to the engineer, the backlog of time-locked transactions were being purposefully designed for a “potentially disruptive mining strategy” involving the theft of miner fees. 

In an interview with CoinDesk, 0xb10c said time-locked transactions represented a “low-priority” problem at present that could eventually balloon to involve the wider network. He explained that fee-sniping would become more lucrative in a few years as the majority of miner income shifts towards transaction fees. 

He continued, 

A fix for this has been released in early 2020. However, it will take a while before all instances of the currently deployed software are upgraded.

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