Ethereum: State of Knowledge and Research Perspectives

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Ethereum: State of Knowledge and

Research Perspectives Sergei Tikhomirov

Motivation Technical overview

Open problems Cryptography Consensus Scalability Privacy Contract programming Other issues Conclusion

Ethereum: State of Knowledge and Research

Perspectives

Sergei Tikhomirov

SnT, University of Luxembourg

24 October 2017 LORIA, Nancy, France

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Outline

Motivation

Technical overview

Open problems Cryptography Consensus Scalability Privacy

Contract programming Other issues

Conclusion

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Why give this talk?

I Ethereum is a fascinating research topic

I Intersection of cryptography, distributed systems, programming languages, privacy, game theory, ...

I Interesting problems of highest practical relevance

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Bitcoin

I A fully decentralized digital currency [Nakamoto 2008]

I Combines cryptography and economics to prevent double spending without a trusted third party

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Ethereum: generalized blockchain

I A blockchain-based application platform [Buterin 2014]

I Key feature: Turing complete programming

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Ethereum features

I Accounts controlled by key or by code (smart contracts)

I Developers write contracts in high-level languages that compile to Ethereum Virtual Machine (EVM) bytecode

I Users interact with contracts via transactions (e.g., send ether, perform computation)

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Ethereum security is hard

I New software stack

I Unfamiliar execution paradigm

I Very limited ability to patch contracts

I Anonymous financially motivated attackers

I Rapid pace of development

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Outline

Motivation

Technical overview

Conclusion

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Cryptography

I Signatures: ECDSA

I Hash for id’s: Keccak-256

I Hash for proof-of-work: Ethash

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Ethash

I A new memory-hard cryptographic hash function

I Developed in 2013–2015, no academic cryptanalysis

I Claims of weaknesses in early versions

I (Ethereum plans to abandon proof-of-work altogether)

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Outline

Motivation

Technical overview

Conclusion

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Consensus: proof-of-work

I Nodes (miners) compete to produce the next block

I Find nonce s. t. hash(nonce|blockheader ) < target

I The first miner to construct a block gets a reward

I Probability of success is proportional to hashing power

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Drawbacks of proof-of-work

I Energy consumption (Bitcoin: #70 ”country”)

I Centralization (benefits from economies of scale)

I Game-theoretic attacks (selfish mining)

These problems are less obvious in Ethereum than in Bitcoin.

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Proof-of-stake as ”virtual mining”

Validators chosen proportionally to stake. Known issues:

I Nothing-at-stake (incentive to mine on all chains)

I Choosing validators (security of randomness source)

I Long-range attacks (finality guarantees)

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Independent evaluation required!

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Outline

Motivation

Technical overview

Conclusion

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Scalability

I Ethereum: 10 tx/sec (Visa: 45k tx/sec)

I Proposed solution: payment channels

I Exchange partially signed tx’s off-chain, settle on-chain

I Payment channel network Raiden is in development

I Related: sharding, fast synchronization

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Outline

Motivation

Technical overview

Conclusion

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Privacy

I All transactions in plaintext, history stored forever

I Blockchain analysis, deanonymization (mostly Bitcoin)

I Possible solution: ZKP / ZkSNARKs (used in ZCash)

I Introduced in Ethereum on 16 October 2017

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Outline

Motivation

Technical overview

Conclusion

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Contract programming in Solidity

Solidity is the most mature high-level contract language.

Example of a simple program:

1 p r a g m a s o l i d i t y 0 . 4 . 1 7 ;

2 c o n t r a c t S t r i n g S t o r a g e C o n t r a c t {

3 s t r i n g p r i v a t e str = " Hello , w o r l d ! ";

4 f u n c t i o n g e t S t r i n g () p u b l i c c o n s t a n t 5 r e t u r n s (s t r i n g) {

6 r e t u r n str ;

7 }

8 f u n c t i o n s e t S t r i n g (s t r i n g _ s t r ) p u b l i c {

9 str = _ s t r ;

10 }

11 }

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Improving code quality

I Summarizing good and bad practices

I Developer tools: code analysis, bug detection

I Formal verification, formalization of EVM

I Safer paradigms, languages, frameworks

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Outline

Motivation

Technical overview

Conclusion

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Other issues

I Governance: who determines Ethereum’s future?

I Usability: friendly dApps for broader audience

I Ethical: what is responsible disclosure in blockchain?

I Legal: how do cryptocurrencies fit in legal systems?

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Conclusion

I Blockchain is still a new technology

I Ethereum poses many research challenges

I Potential is enormous

I Security issues are inevitable

Researchers are welcome!

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Questions?

I

cryptolux.org

I

Ethereum: State of Knowledge and Research Perspectives

Ethereum: State of Knowledge and Research

Perspectives

Outline

Why give this talk?

Bitcoin

Ethereum: generalized blockchain

Ethereum features

Ethereum security is hard

Outline

Cryptography

Ethash

Outline

Consensus: proof-of-work

Drawbacks of proof-of-work

Proof-of-stake as ”virtual mining”

Outline

Scalability

Outline

Privacy

Outline

Contract programming in Solidity

Improving code quality

Outline

Other issues

Conclusion

Researchers are welcome!

Questions?

cryptolux.org

s-tikhomirov.github.io