Intro
Preface
Contents
Chapter 1 Introduction
Chapter 2 Consensus in Blockchain
2.1 A Brief History
2.2 What is Blockchain?
2.2.1 The blockchain abstraction as a directed acyclic graph
2.2.2 Signed transactions
2.2.3 Distributed implementation of the blockchain abstraction
2.3 Double spending
2.3.1 Forks as disagreements on the blocks at a given index
2.3.2 From forks to double spending
2.3.3 How to avoid forks?
2.4 Conclusion
2.5 Bibliographic notes
2.6 Exercises
References
Chapter 3 Blockchain Fundamentals
3.1 Introduction

3.2 Failures and communication
3.3 Properties of consensus
3.4 Impossibility to solve consensus in asynchronous networks
3.4.1 Failure detectors
3.4.2 Randomized consensus
3.4.3 Deterministic termination
3.4.4 Additional synchrony
3.4.5 Impossibility to solve consensus with too many failures
3.5 Proof of work and mining
3.5.1 Proposing to the consensus
3.5.2 Decided blocks and committed transactions
3.6 Resolving forks
3.7 The 51% Attack
3.8 The GHOST protocol
3.9 Conclusion
3.10 Bibliographic notes
3.11 Exercises
References

Chapter 4 Consensus Fundamentals
4.1 Introduction
4.2 Consensus without failures
4.2.1 Consensus algorithm without failures and with synchrony
4.2.2 Correctness of the consensus algorithm without failures
4.2.3 Complexities of the consensus algorithm without failures
4.3 Consensus with crash failures
4.3.1 Correctness of the consensus algorithm with crash failures
4.3.2 Complexity of the consensus algorithm with crash failures
4.4 Consensus with Byzantine failures
4.4.1 The problem of consensus with Byzantine failures
4.4.2 The EIG algorithm

4.4.3 Example with n = 4 and f = 1
4.4.4 Complexity of the EIG algorithm
4.5 Conclusion
4.6 Bibliographic notes
4.7 Exercises
References
Chapter 5 Making Blockchains Secure
5.1 Introduction
5.2 Beyond synchrony
5.3 The Balance Attack
5.4 Double spending in Ethereum
5.4.1 Double spending is easy in case of route hijacking
5.4.2 Partitioning Ethereum mining pools turns out to be hard
5.5 Proof-of-Authority and permissioned sealers of Ethereum
5.5.1 The Aura algorithm
5.5.2 The Attack of the Clones
5.6 Accountability
5.7 Conclusion

5.8 Bibliographic notes
5.9 Exercises
References
Chapter 6 Making Blockchains Scale
6.1 Introduction
6.2 Consensus without synchrony
6.2.1 The seminal Practical Byzantine Fault Tolerance
6.2.2 Complexities
6.2.3 Changes required by the scale of the consensus network
6.3 Leveraging bandwidth
6.3.1 The time complexity of a leader-based propagation
6.3.2 The time complexity of a leaderless propagation
6.3.3 Bypassing the leader bottleneck with the superblock optimization
6.4 The Set Byzantine Consensus problem
6.5 Democratic Byzantine fault tolerance