The paper "Majority is Not Enough: Bitcoin Mining is Vulnerable" by Ittay Eyal and Emin Gün Sirer from Cornell University addresses the security vulnerabilities of Bitcoin's mining protocol. The authors argue that the Bitcoin protocol is not incentive-compatible, meaning that colluding miners can gain an unfair advantage over honest miners. They introduce a strategy called "Selfish Mining," where a group of colluding miners can keep their discovered blocks private, creating a fork in the blockchain. This strategy allows the selfish miners to waste honest miners' resources on blocks that will not be included in the main chain, leading to higher rewards for the selfish miners. The paper shows that as the size of the selfish pool increases, its revenue rises superlinearly, and rational miners will prefer to join the selfish pool, potentially leading to a majority of miners being colluding. The authors propose a backward-compatible modification to the Bitcoin protocol that sets a threshold for the pool size, making it difficult for a selfish pool to gain control. They conclude that the current Bitcoin system is vulnerable to such attacks and recommend immediate implementation of their proposed fix to maintain the decentralized nature of the currency.The paper "Majority is Not Enough: Bitcoin Mining is Vulnerable" by Ittay Eyal and Emin Gün Sirer from Cornell University addresses the security vulnerabilities of Bitcoin's mining protocol. The authors argue that the Bitcoin protocol is not incentive-compatible, meaning that colluding miners can gain an unfair advantage over honest miners. They introduce a strategy called "Selfish Mining," where a group of colluding miners can keep their discovered blocks private, creating a fork in the blockchain. This strategy allows the selfish miners to waste honest miners' resources on blocks that will not be included in the main chain, leading to higher rewards for the selfish miners. The paper shows that as the size of the selfish pool increases, its revenue rises superlinearly, and rational miners will prefer to join the selfish pool, potentially leading to a majority of miners being colluding. The authors propose a backward-compatible modification to the Bitcoin protocol that sets a threshold for the pool size, making it difficult for a selfish pool to gain control. They conclude that the current Bitcoin system is vulnerable to such attacks and recommend immediate implementation of their proposed fix to maintain the decentralized nature of the currency.