Ethereum : Ghost Protocol (Greedy Heaviest Observed Subtree)

The GHOST protocol (Greedy Heaviest Observed Subtree) is a chain selection rule that is used in the Ethereum blockchain. It is a modification of the longest chain rule, which was the original chain selection rule used in Ethereum.

 

The GHOST protocol was introduced in 2013 as a way to improve the security of the Ethereum blockchain. It does this by making it more difficult for attackers to mine empty blocks (blocks that contain no transactions).

 

Under the longest chain rule, the longest chain is always considered to be the valid chain. This means that attackers can mine empty blocks and then add them to the longest chain, even if the empty blocks are not valid.

 

The GHOST protocol prevents this by giving rewards to miners who mine blocks that are included in the heaviest subtree. The heaviest subtree is the subtree that contains the most cumulative difficulty. This means that attackers will not be able to mine empty blocks and add them to the longest chain, because the empty blocks will not have any cumulative difficulty.

 

The GHOST protocol has been shown to be effective in improving the security of the Ethereum blockchain. It has made it more difficult for attackers to mine empty blocks and to launch 51% attacks.

 

Here are some of the benefits of the GHOST protocol:

• Security: The GHOST protocol improves the security of the Ethereum blockchain by making it more difficult for attackers to mine empty blocks and to launch 51% attacks.
• Decentralization: The GHOST protocol helps to decentralize the Ethereum blockchain by making it more difficult for large mining pools to control the network.
• Fairness: The GHOST protocol is fair because it rewards miners based on the cumulative difficulty of the blocks that they mine.

Overall, the GHOST protocol is an important part of the Ethereum blockchain. It helps to improve the security, decentralization, and fairness of the network.

Feature	Longest chain rule	GHOST protocol
Chain selection rule	Selects the longest chain as the valid chain.	Selects the heaviest subtree as the valid chain.
Security	Vulnerable to empty blocks and 51% attacks.	More secure against empty blocks and 51% attacks.
Decentralization	Can be centralized by large mining pools.	More decentralized than the longest chain rule.
Fairness	Miners are rewarded based on the number of blocks they mine, even if the blocks are empty.	Miners are rewarded based on the cumulative difficulty of the blocks they mine.

https://medium.com/coinmonks/an-in-depth-look-at-the-ghost-protocol-part-2-how-ghost-works-50e49edf7a52