New Research Shows How Ethereum Miners Execute Consensus-Level Attack to Earn More

A new research paper published by The Hebrew University in Israel titled “The first evidence of a consensus-level attack on a major cryptocurrency” shows how miners manipulate the network to earn more.

Aviv Yaish, a crypto-focused researcher at the University, shared the paper on Twitter on the 5th of August 2022. The paper, which is currently waiting for peer review, leverages publicly available on-chain data and the open source codebase of Ethereum to deduce its conclusions.

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In the thread of tweets, Aviv Yaish, who is one of the authors of the paper, highlighted how F2Pool’s block timestamps are artificially altered to boost rewards.

The researcher stated that the difficulty of mining the current block changes on the fly, and decreases the longer time passes without anyone mining a new valid block, in order to keep inter-block time moderately low.

Yaish wrote:

“The time between blocks, and thus also mining difficulty, is determined according to block timestamps. The problem with this is that according to Ethereum’s consensus laws miners have a certain degree of freedom when setting them, and can even set false timestamps…

“The same consensus laws say that in case of ties between blocks of the same height, the block with a higher total mining difficulty should be picked to be the parent of the currently mined block, while the other one should be its uncle…”

So, a miner who desires to replace the last block on the blockchain can mine its own block that has a timestamp low enough to increase the mining difficulty of the block. This is used, especially when the last block has high-paying transactions or double-spend transactions in the block.

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He said a miner can “even preemptively mine blocks with such timestamps to make sure they win in case of ties with other blocks which might be mined concurrently, or which might’ve been mined but haven’t reached the attacker yet.”

So, the Israeli University researchers discovered that anytime F2Pool’s block timestamps attain the point where mining difficulty is expected to decrease, miners artificially set them to be one second earlier. The research paper shows that miners have been secretly executing this attack over the past two years.

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