# Analysis of Ethereum GHOST Agreement

GHOST is called Greedy Heaviest-Observed Sub-Tree, the most observable subtree protocol for greed. Unlike the longest chain principle in Bitcoin, Ethereum uses the GHOST protocol to determine the main chain by judging the heaviest subtree.

## Algorithm Description

Algorithm for selecting a block as the main chain

``Input: Block tree T 1. set B ← Genesis Block 2. if ChildrenT (B) = ∅ then return(B) and exit 3. else update B ← argmax |subtreeT (C)| C∈ChildrenT (B) 4. goto line 2` `

ChildrenT (B) returns the set of sub-blocks of B; subtreeT(C) returns the weight of the root tree with C

Beginning with the Genesis block, initialize B to the genesis block;

Determine whether the subtree of B is an empty set, and if it is empty, indicating that no subblock is currently the main chain, return B block and exit;

Otherwise update B is the sub-block with the heaviest subtree;

Go to step 2 and continue to find the next block of the main chain;

## Ethereum and Bitcoin's main chain selection

The block weight is the number of valid blocks in the tree root (difficulty accumulation)

As can be seen from the above figure, using the longest chain principle in Bitcoin, 0<-1B<-2D<-3F<-4C<-5B is the longest main chain; the most heavy subtree principle is used in Ethereum 0<-1B <-2C<-3D<-4B is the heaviest main chain

## Uncle block reward

Basic content :

1. The main chain block gets the basic reward (3Eth)

2. One block refers to at most two unblocks

3. Contains a non-block to get 1/32 of the mining reward

Calculation formula :

` `((叔块高度+8-当前块的高度)/8 )*base reward` `

The transaction fee is not assigned to the uncle block. The difference between the current block height and the uncle block height is 8 (or more).

1. Security is independent of the block speed, which guarantees the expansion of GHOST (no reduction in interval due to reduced time, up to 200tps)

2. Solve the problem of lone block reward and encourage miners to participate in the block

3. Demonstrate that blindly increasing TPS is not feasible by increasing the block rate and block size.

## summary

The ghost protocol uses the most heavy chain principle to improve system security;

Increased the reward for the uncle block and encouraged the miners to participate;

However, the current tps is still not high (10-20) and requires the participation of other expansion plans;