Abstract:

As the success of The Merge has brought Ethereum to the Proof-of-Stake consensus, the staking mechanism has changed many facets of the Ethereum community of validators. In theory, PoS Ethereum is superior in energy saving and decentralization compared with the former PoW Ethereum, preserving security in the consensus-building process by blockchain validation. However, reality speaks louder in data visualizations. In this project, we implemented three visualizations of the validator life cycle based on web3.py Ethereum blockchain data and Beacon block data to evaluate PoS Ethereum consensus decentralization and security.

Part I: Introduction

With the success of The Merge, Ethereum has finished the joining of the execution layer and the consensus layer, the Beacon Chain, upgrading from the Proof-of-Work (PoW) consensus to Proof-of-Stake (PoS) consensus. The staking mechanism in the PoS Ethereum miners on the Ethereum consensus layer into validators. The validators stake ethers (ETH) into a smart contract, contributing to the PoS consensus. We elaborate on the life cycle of a validator and how a validator takes part in the Ethereum PoS consensus. 

Figure 1 shows the block finalization rate before and after The Merge. The x-axis shows the time series, while the y-axis shows the time of block finalization in seconds. The block finalization rate is stable between 13-13.5 seconds per block during 2021 and the first half of 2022. It peaked in June 2022 and dropped sharply at the beginning of July. After The Merge, the average block finalization time drops to 12 seconds per block. 

The staking mechanism on the PoS Ethereum contributed essentially to the change of block finalization duration after the merge. On the previous PoW Ethereum, miners compete in computing the hash code to mine a block, where the block finalization duration depends mainly on the computing powers. In contrast, on the PoS Ethereum, the finalization happens during the validation of transactions in a block, which occurs in a slot of 12 seconds. Thus, in facets of blockchain building and finalization, the PoS mechanism brings much efficiency to Ethereum. First, the new staking mechanism reduces the energy waste caused by mining. Second, the new validation process improves efficiency in the block finalization rate, contributing to scalability by accelerating the block-building process. Validators are the casting stars of the PoS Ethereum. Below, we introduce further the life cycle and contribution of validators in the PoS consensus.

1.1. What is the validator life cycle?

Figure 2 shows a generalized validator life cycle on the PoS Ethereum blockchain. According to Ethereum notes and Ethereum Developer Docs, validators are in one of the six states: 1) deposited, 2) eligible to be activated (pending), 3) activated, 4) slashed, 5) exited, and 6) withdrawable. The PoS Ethereum times in slots, each of 12 seconds, and epochs, each epoch of 32 slots (6.4 mins). Ethereum updates the state of validators by epoch (s) following the rules below.

• Deposited: after paying the deposit fee of 32 ETH, the validator becomes deposited

• Eligible to be activated: the first step in the epoch-processing is to check whether the validator is eligible to be added to the activation queue. The activation queue locates validators who are eligible for activation but are not activated yet. 

• Activated: for validators entering the activation queue after one epoch, if checked to be eligible for activation, the validators would be activated after four epochs. Once activated, the validators are able to participate in the PoW consensus process. 

• Slashed: the validator misbehaving and caught by other validators are slashed.

• Exited: the validators are exited if they are slashed or have an insufficient balance due to large penalties or volunteer to exit. 

• Withdrawable: the unslashed (and exited) validators have a lock-in period of 2⁸ epochs (~27 hours) to become withdrawable; in contrast, the slashed (and existed) validators need to wait from 2¹³ epochs (~36 days) before they become withdrawable. 

1.2. How do validators take part in the PoS Ethereum consensus?

Validators propose and validate blocks on the PoS Ethereum blockchain. At each epoch, the mechanism randomly selects validators into proposers and a committee of attesters. In each slot, the proposer proposes a block, and the committee votes for the validity of the proposed block.

Part II Research Questions

However, how the merge changes Ethereum, in reality, is not visible to the public. Reality speaks louder in data visualizations. Thus, we implement three visualizations of the beacon chain before and after the merge so that the general public would be able to infer the answer to three important research questions. 

• RQ1 (the casting stars): What is the time series distribution of validators’ life cycles on Ethereum?

• RQ2 (consensus decentralization): How decentralized is the voting mechanism in the Proof-of-Stake Ethereum?

• RQ3 (consensus security): How does the staking mechanism prevent malicious behaviors?

Our research goals are to:

1. Help our audience understand how proof-of-stake Ethereum works by visualizing the life cycle of the casting star, the validators.

2. Verify the decentralization in PoS Ethereum by visualizing the validators’ voting process.

3. Examine the power of the staking mechanism in improving consensus security by showing the change in the number of slashed validators before and after The Merge. 

Part III: Methodology

Data and Code Availability: The data, code, and visualizations are available on GitHub: https://github.com/SciEcon/beacon-chain-merge

3.1. The River Plot for Research Question 1

For RQ1, we draw a river plot to show the times series distribution of validators in different states of their life cycles.

Query Data: We retrieved validator information using the web3py library. The data consists of information on 427927 validators. Figure 3 shows a validator data entry example.

Process Data: To clarify our findings, we focus on three main periods in a validator’s life cycle: 1) being eligible for activation, 2) being activated, and 3) being existed. The raw data consists of the epochs for which a validator was eligible-to-activate, activated, withdrawable, or exited. From these, we aggregated the validator data entry daily, resulting in Table 1.

Table 1: The features and descriptions of data for RQ1.

3.2. The Chord Plot for Research Question 2

For RQ2, we draw a chord graph that connects block attestors to the proposer. 

Query Data: For this purpose, we collected two sets of data:

The first dataset is the beacon chain block data ranging from Slot No. 4680000 to 4720000 (40001 blocks in total). I retrieved the data using the ethereum2-etl library. Figure 4 shows a block data entry example. For each block, we retrieved the identity of the block proposer and epoch committees (attestors) index using the variables of proposer_index and attestations, respectively.

The second dataset documents the epoch committees for each corresponding blocks. We retrieve the data using get_epoch_committees API from web3py library. We provide an epoch committee data entry example item in Figure 5.

3.3. Line Charts for Research Question 3

For RQ3, we draw two line charts to illustrate and compare the block time and slashing conditions before and after the merge. We retrieved two datasets:

Dataset 1: We query block time history data from etherescan public dashboard. Figure 6 shows the example data.

Dataset 2: We reused the status data shown in Table 1 to calculate the number of validators being slashed. Table 3 shows one entry example of the processed data. 

Part IV: Results

4.1. The Result 1 River Plot

Figure 7 and Figure 8 show the time series distribution of validator life cycles. Figure 7 demonstrates the changes in the amount of eligible-for-activation (green area), activated (red area), and exited (black area) validators from Dec. 4th, 2020, to Oct. 28th, 2022. Figure 8 demonstrates only the distribution of eligible-for-activation (green area) and exited (black area) validators. From the figure, we have two observations:

• the number of activated validators is increasing stably

• there are four periods in the history when the number of new eligible participants increased sharply: 12/04/2020–03/06/2021, 05/03/2021–07/20/2021, 08/16/2021–09/21/2021, and 03/01/2022–05/31/2022.

4.2. The Result 2 Chord Graph

Figure 9 is a chord graph for the attestation in block-building. This chord graph connects block attesters to the corresponding block proposer. The left side represents the four blocks proposed in 4 separate slots, labeled with the IDs of the block proposer. And The right side represents the IDs of all the attesters who contribute to validating each block. Figure 9 shows that, with the fixed deposit fee of 32 ETH and equal voting power of all the validators, the actual voting contribution is equally distributed among all the validators, evidence of realized consensus decentralization.

4.3 The Result 3 Line Chart

Figure 10 shows the changes in the (accumulated) slashed validators before and after The Merge. The x-axis demonstrates the timeline from late 2020 to Oct. 2022; The (left) right y-axis illustrates the number of (accumulated) slashed validators on-chain. Figure 10 evidences a sharp increase in the accumulated number of slashed validators from Feb. 2nd, 2021, to Feb. 6th, 2021. The number of slashed validators oscillated before the merge, soared right after the merge, and then decreased to and stayed around zero. Our results imply an increased consensus security on PoS Ethereum after the merge.

Part V: Reflections and Afterword

In conclusion, on the PoS Ethereum, stakeholders contribute to the consensus-building process by staking 32 ETH and acting as validators. Theory speaks: PoS Ethereum is superior in energy saving and decentralization compared with the former PoW Ethereum, preserving security in the consensus-building process by blockchain validation. How about the reality? Our visualization speaks louder: the merge evidences an improvement in consensus decentralization and security. 

Let this be our last word. The staking mechanism in PoS Ethereum resonates with the wisdom in the Art of War:

Thus the highest form of generalship is to balk at the enemy's plans; the next best is to prevent the junction of the enemy's forces; the next in order is to attack the enemy's army in the field, and the worst policy of all is to besiege walled cities. (Original text in Chinese: 故上兵伐謀，其次伐交，其次伐兵，其下攻城.)

In similar spirits, the highest form of slashing is to incentivize the players not to be slashed at all…