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Analyzing Geospatial Distribution in Blockchains
- 1. Analyzing Geospatial Distribution in Blockchains Shashank Motepalli and Hans-Arno Jacobsen IEEE International Conference on Decentralized Applications and Infrastructures (IEEE DAPPS 2023)
- 2. IEEE DAPPS 2023 Why blockchains? Source: ChatGPT 2
- 3. IEEE DAPPS 2023 The Pinnacle of Decentralization? Often overlooked, but easily measurable dimension: Geospatial distribution in consensus 3 Society Crypto Economics Political Sciences Blockchain Decentralization Technology
- 4. IEEE DAPPS 2023 Geospatial Distribution of Validators in Ethereum 69.91% of total validators in two regions, namely the US and Germany Data: Accessed on November 23, 2022 https://etherscan.io/nodetracker 4
- 5. IEEE DAPPS 2023 Geospatial Distribution of Validators in 0L.network Data: Epoch 317 on 0L.network 5
- 6. IEEE DAPPS 2023 Why More Geospatial Distribution? 1. Robustness 1. Fairness 1. Regulations 6
- 7. IEEE DAPPS 2023 The Challenge: Geospatial Centralization 01 Analyze geospatial distribution of validators at consensus layer 02 Understand if consensus protocols inhibit geospatial distribution 03 Address the factors restraining geospatial distribution 7 Hypothesis: Geospatially distant validators (minority) are marked as crash failures
- 8. IEEE DAPPS 2023 Our Approach GeoDec tool to emulate consensus protocol with arbitrary locations Prove geospatially distant (minority) validators are disadvantaged Address concerns of minority validators with our solution 8
- 10. IEEE DAPPS 2023 Classical BFT Blockchains block#123 block#125 block#126 10 Reach a quorum Validators Proposer #126 Epoch 28 Validator rewards Block is appended
- 11. IEEE DAPPS 2023 Measuring Validator Performance To counter free-riding and nothing at stake problems, validators with liveliness less than a threshold are penalized Liveliness = Number of blocks signed by a validator Total number of blocks committed in an epoch Motepalli, S., & Jacobsen, H. A. (2021, September). Reward mechanism for blockchains using evolutionary game theory. In 2021 3rd Conference on Blockchain Research & Applications for Innovative Networks and Services (BRAINS) (pp. 217-224). IEEE. 11
- 12. IEEE DAPPS 2023 GeoDec Emulator 12
- 13. IEEE DAPPS 2023 GeoDec Emulator 13 ● Local compute cluster ● netem for induced latencies ● Hotstuff consensus protocol ● Outputs liveliness
- 14. IEEE DAPPS 2023 GeoDec Emulations Replicate the behaviour observed in 0L 14
- 15. IEEE DAPPS 2023 Measures how distant a validator is from rest of the validators Only consider the quorum Haversine distance between the validators is considered GDI values depends on all the validators, so changes with epoch Geospatial Diversity Index (GDI) 15
- 16. IEEE DAPPS 2023 Minority Validators are Punished 16
- 17. IEEE DAPPS 2023 Minority Validators Have the Lowest Liveliness 17 Two cases
- 18. IEEE DAPPS 2023 Empirical Evidence n = 16 validators 167 runs of 5 epochs each 18
- 19. IEEE DAPPS 2023 Saving the Minority Validators 19
- 20. IEEE DAPPS 2023 GDI Exception Smart Contract 20
- 21. IEEE DAPPS 2023 GeoDec Evaluations 21 ● n = 16 ● Quorum formed in US and Europe ● Randomly choose validators from 242 cities
- 22. IEEE DAPPS 2023 Evaluations on 64 node cluster 22
- 23. IEEE DAPPS 2023 To Conclude Designed and developed GeoDec emulator Minority validators are disadvantaged (punished) in consensus protocols We present GDI smart contract to preserve higher geospatial distribution 23
- 24. IEEE DAPPS 2023 Thank you! 24 Questions? https://arxiv.org/abs/2305.17771 https://github.com/sm86/geodec-hotstuff Resources:
Editor's Notes
- Hello everyone, I am Shashank. PhD student in Computer Engineering at University of Toronto. I am here to present my work at MSRG with my advisor Prof. Arno Jacobsen. Before we dive in, let us ask some important questions.
- What are the first things that come to your mind when you hear the word blockchain. We asked ChatGPT the same question, look at its response. What catches my attention here is the term decentralization. Decentralization is at heart of blockchains. If we do not care of decentralization, we have already solved most problems in centralized systems. Decentralization adds all the complexity. Later: Maybe I need to cite ChatGPT
- Decentralization is a complex concept involving social, economic and political dimensions on top of its technology. A lot of attempts are made lately to quantify decentralization but its difficult to measure all its dimensions. In this work, we want to consider one often overlooks but easily measurable dimension - the geospatial distribution in the consensus protocols. I.e., how the participants are distributed in a blockchain.
- Let us see validator distribution on Ethereum, a major blockchain. As we can see the validators are mainly concentrated in two regions, namely US and Germany. Distribution is similar when I checked it recently too.
- Is it Ethereum problem? No it is similar distribution in even other blockchains, such as 0L. As we can see, most validators are located in US and Finland, none outside North America and Europe. This makes us question if other validators are being neglected by the protocols. We observed validators joined from Singapore and Australia but were dropped next epoch. With that being said, let us understand if geospatial distribution is really important?
- IEEE DAPPS slide number Images with points Why do we need more geospatial distribution? Firstly robustness Secondly fairness Use some statements and examples from Notes below. Let us now move on to the problem in hand. NOTES: Firstly, boosting geospatial diversity contributes to the \textit{robustness} of the blockchain. In other words, the blockchain would be more resilient to downtimes caused by various factors, such as the lack of electricity required for computation, changing regulations, and even wars. Imagine most validators of a blockchain network located at a data center that does not adhere to fire safety or is prone to natural calamities. This situation is not far from reality; for instance, in September of 2021, an outage at an AWS data center could bring down the entire Solana blockchain~\cite{amazonSolana}. Even worse, a cloud provider chooses to bring down 40\% of all validators of a live blockchain for not adhering to its policies~\cite{HetznerSolana}. Secondly, geospatial diversity facilitates \textit{fairness} of the blockchain resources, notably for time-critical operations, by lowering latencies and providing equitable access to users from all geographic regions. For illustration, consider the advantages of arbitrage traders on a decentralized exchange, such as UniSwap~\cite{adams2021uniswap}, due to geographic proximity to validators. Thirdly, promoting geospatial diversity can reduce the burden to comply with regulations of judridictions the validators do not belong to. For instance, according to SEC, everyone who does transactions on Ethereum falls under the US Jurisdiction because the US has around half of the network's validators~\cite{SECEthereum}. This practice is worrisome as one might break the law without being aware of the blockchains' underlying infrastructure.
- What are we trying to achieve in this work? Firstly, there is little to no studies focusing on geospatial distribution of validators and dissection of consensus protocols. Secondly, understand if there are factors leading to geospatial centralization. Finally, we address the factors leading to more geospatial distribution We look at consensus layer and only on geospatial locations, not data centre companies.
- Blockchains can be classified into two types based on how they achieve finality. We are interested in ones with deterministic finality, i.e., classical consensus protocols. We have a set of validators participating in the consensus protocol, fixed for an epoch. One initiates transaction by sending it through the client, one of the validator would propose the transaction to others. We need a quorum. We are looking to latest ones such as HotStuff - where we have optimistic responsiveness - we do not wait for everyone. PoS can have these as underlying protocol
- Reward mechanism plays important role in consensus. Quorum based consenus open up some attack vectors such as free riding problem and nothing at stake problem. To address these, we only reward validators who participate in consensus protocols. We use liveliness as a measure to participate performance of validator. Penalization either in terms of penalty or jailing.
- Let us now look into our emulator
- We run core consensus protocol, HotStuff, on compute canada cluster. To mimic the WAN, we use pairwise latencies given by WonderProxy Netem tool helps us emulate these latencties between the nodes. So given the input in cities. We use netem to emulate the WAN and run the performance metrics.
- Provide the intuition for the proof.
- Make minimal changes and easily deployable - we used a smart contract. Provides same security as underlying protocol.