Public Blockchains Proof-of-Work Consortium & Private - PowerPoint PPT Presentation

1200 × 700 The Attack of the Clones against Proof-of-Authority Parinya Ekparinya Vincent Gramoli Guillaume Jourjon Ekparinya et al, "The Attack of the Clones against PoA" Page 1

Public Blockchains Proof-of-Work Consortium & Private Blockchains Ekparinya et al, "The Attack of the Clones against PoA" Page 2

Public Blockchains Proof-of-Work Consortium & Private Blockchains Proof-of-Authority Ekparinya et al, "The Attack of the Clones against PoA" Page 3

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Why Proof-of-Authority (PoA)? Ekparinya et al, "The Attack of the Clones against PoA" Page 6

Why Proof-of-Authority (PoA)? Ekparinya et al, "The Attack of the Clones against PoA" Page 7

Why Proof-of-Authority (PoA)? Ekparinya et al, "The Attack of the Clones against PoA" Page 8

Why Proof-of-Authority (PoA)? BFT Ekparinya et al, "The Attack of the Clones against PoA" Page 9

Why Proof-of-Authority (PoA)? BFT Ekparinya et al, "The Attack of the Clones against PoA" Page 10

The Cloning Attack => Double-spending $ 10 $ 10 Ekparinya et al, "The Attack of the Clones against PoA" Page 11

The Cloning Attack => Double-spending SAME TOKENS!! $ 10 $ 10 Ekparinya et al, "The Attack of the Clones against PoA" Page 12

Q: How is it possible to double spend on PoA/Ethereum? Ekparinya et al, "The Attack of the Clones against PoA" Page 13

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers Ekparinya et al, "The Attack of the Clones against PoA" Page 14

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers Ekparinya et al, "The Attack of the Clones against PoA" Page 15

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 Blocks Ekparinya et al, "The Attack of the Clones against PoA" Page 16

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 2 Blocks Ekparinya et al, "The Attack of the Clones against PoA" Page 17

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 2 Blocks Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 18

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 2 3 Blocks Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 19

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 2 3 Blocks Decided Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 20

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 2 3 4 Blocks Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 21

The Modus Operandi of AuRa N4 N1 N2 N3 N5 Sealers 1 2 3 4 5 Blocks Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 22

The Modus Operandi of AuRa N4 N2 N3 N5 N1 Sealers 1 2 3 4 5 6 Blocks Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 23

The Modus Operandi of AuRa ZZz N4 N3 N5 N1 N2 Sealers 1 2 3 4 5 6 Blocks Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 24

The Modus Operandi of AuRa ZZz N4 N5 N1 N2 N3 Sealers … 1 2 3 4 5 6 7 Blocks Decided Time (s) 5 10 25 30 40 15 20 35 Ekparinya et al, "The Attack of the Clones against PoA" Page 25

N3 … 7 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 26

N4 N1 N3 Group A Sealers Group A Blocks … 7 Group B Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 27

N4 N1 N3 Group A Sealers Group A 8 Blocks … 7 Group B Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 28

N4 N1 N3 Group A Sealers Group A 8 Blocks … 7 Group B 8 Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 29

N4 N1 N3 Group A Sealers Group A 9 8 Blocks … 7 Group B 8 Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 30

N4 N1 N3 Group A Sealers Group A 9 8 Blocks … 7 Group B 8 9 Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 31

N4 N1 N3 Group A Sealers Group A 9 8 10 Blocks … 7 Group B 8 9 Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 32

N1 N4 N3 Group A Sealers Group A 9 8 10 11 Blocks … 7 Group B 8 9 Blocks Group B Sealers N5 N2 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 33

N1 N4 N3 Group A Sealers Group A 9 8 10 11 Blocks … 7 Group B 8 9 10 Blocks Group B Sealers N2 N5 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 34

N1 N4 N3 Group A Sealers Group A 9 8 10 11 Blocks … 7 Group B 8 9 10 Blocks Group B Sealers N2 N5 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 35

N4 N3 Group A Sealers N1 Group A 9 8 10 11 Blocks … 7 12 Group B Blocks Group B Sealers N2 N5 Time (s) 60 65 75 40 45 50 55 70 Ekparinya et al, "The Attack of the Clones against PoA" Page 36

Block decision duration network partition – Since decision requires strictly more than half, only one partition may decide blocks Can decide a block Ekparinya et al, "The Attack of the Clones against PoA" Page 37

Block decision duration network partition – Since decision requires strictly more than half, only one partition may decide blocks Can decide a block Ekparinya et al, "The Attack of the Clones against PoA" Page 38

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If one sealer become malicious – A malicious sealer creates a clone to participate in both partitions!! – If n = 9, both partitions contain 5 sealers, therefore both may decide a block!! Malicious Clone sealer sealer Can Can decide decide a block a block Ekparinya et al, "The Attack of the Clones against PoA" Page 40

The Cloning Attack Ekparinya et al, "The Attack of the Clones against PoA" Page 41

The Cloning Attack Ekparinya et al, "The Attack of the Clones against PoA" Page 42

The Cloning Attack Ekparinya et al, "The Attack of the Clones against PoA" Page 43

The Cloning Attack Ekparinya et al, "The Attack of the Clones against PoA" Page 44

The Cloning Attack Ekparinya et al, "The Attack of the Clones against PoA" Page 45

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Countermeasure – The algorithm will be more resistant to the attack if it requires strictly more than two- thirds to decide a block as shown in the illustration below with n = 9 sealers. Cannot Cannot decide decide a block a block Ekparinya et al, "The Attack of the Clones against PoA" Page 52

Key takeaways – With the attack of the Clones, it is possible to double spend in PoA/Ethereum. – Provided sufficient network partition duration, the attacker can double spend with 100% success rate. – To promote safety property in PoA/Ethereum: the higher number of required sealers, the higher resistance against the attack. – The attack applies as well to Clique. The details can be found in paper. – We exchanged with the security experts of geth and parity. The developers of xDai have already took this attack into account in their POSDAO consensus algorithm. Ekparinya et al, "The Attack of the Clones against PoA" Page 53