What is a Selfish Mining Attack? How it Works & Ways to Prevent it

What is a Selfish Mining Attack?

In Bitcoin, a selfish mining attack is a sophisticated maneuver by which crypto miners – or, more commonly, a group of collaborating miners – engage in a deliberate process to gain a disproportionate advantage over other miners on a blockchain network.

Techopedia Explains

In essence, a selfish mining attack is achieved by withholding the broadcast of newly mined blocks to the public network. By doing so, these miners can clandestinely continue to mine the subsequent block, getting a head start and increasing their chances of adding more blocks to the chain.

This secretive approach disrupts the typical transparent operation of the blockchain.

Usually, when a miner successfully mines a block, they broadcast this achievement to the entire network, ensuring synchronization and consistency across the chain.

However, in a selfish mining scenario, by keeping their mined blocks hidden, selfish miners create a scenario where two versions of the truth exist: their private, undisclosed version and the version the rest of the network is aware of.

The strategy behind such a devious approach is twofold:

• Firstly, it allows the selfish miner to potentially earn more rewards, as they can maintain a lead in the mining process.
• Secondly, and more detrimentally, it causes other unsuspecting miners to waste computational resources on blocks that, unbeknownst to them, are already behind in the race.

This not only diminishes the rewards for honest miners but also compromises the security and integrity of the blockchain network, challenging the principles of fairness and transparency upon which the technology is built.

How Does a Selfish Mining Attack Work?

To grasp the mechanism of a selfish mining attack, one needs to understand the basic proof-of-work (PoW) mining process.

In cryptocurrency, miners compete to solve complex mathematical puzzles. The winner validates the transactions, adds the block to the public chain, and receives a reward.

However, in a selfish mining attack, it works in a different way:

1. The selfish miner competes and successfully mines a block.
2. Rather than broadcasting this block to the network, they keep it private, creating an accidental fork – a series of blocks running parallel to the blockchain.
3. While honest miners toil on the main chain, the selfish miner continues to mine blocks on their secret fork.
4. The aim is to have a longer private chain. Once this is achieved, they disclose their secret fork.
5. The network always recognizes the longest chain as the most valid.
6. If the selfish miner’s chain is longer, it gets adopted, and the honest miners’ blocks are discarded, causing them to lose their rewards.

Is a Selfish Mining Attack Against Bitcoin Possible?

While the concept of selfish mining was theorized as early as 2010, it was illuminated through a paper by Cornell University researchers Eyal and Sirer.

They proposed a two-stage attack where initially, the selfish miner would alter incentives, and neutral miners, enticed by potential profits, might join the selfish miner, ultimately risking a 51% attack.

However, implementing such an attack on Bitcoin is challenging.

• First, the attacker needs a significant amount of computational power to make their private chain the longest.
• Second, the Bitcoin community, being watchful and ideologically driven, would likely resist efforts to undermine the network.

An overt intention to perform such an attack could lead to a mass exodus from an implicated mining pool, nullifying the threat.

How to Prevent Selfish Mining Attacks?

There are two predominant methods used to mitigate the risk of a selfish mining attack, including:

• Randomization Technique: This approach requires miners to randomly select which fork to work on when multiple forks are present. Furthermore, miners need to reveal details of all found blocks and forks. The unpredictability of this process negates the selfish miner’s advantage.
• Timestamping: Assigning a timestamp to each mined block is another countermeasure. Blocks mined in secrecy and later introduced to the main chain can be identified and rejected based on out-of-date timestamps.

However, to holistically thwart the threat, a more dynamic and comprehensive network response, emphasizing both technological and community-driven solutions, is crucial.

The Bottom Line

Selfish Mining Attacks, while theoretically feasible, are complex to execute, especially on mature and vigilant networks like Bitcoin.

The core strength of blockchain lies in its decentralized nature and the community that surrounds it.

As long as the community remains watchful and proactive, potential threats can be identified and countered, maintaining the integrity and security of the network.