How to Hack Blockchain Systems Parinya Ekparinya Vincent Gramoli - PowerPoint PPT Presentation

How to Hack Blockchain Systems Parinya Ekparinya Vincent Gramoli Guillaume Jourjon The University of Sydney Page 1

Blockchain Block #41 Block #42 Block #43 Block #44 Proof: Proof: Proof: Proof: 0xd00d1e… 0xc0ffee… 0xf00baa… 0xfabfab… Parent Proof: Parent Proof: Parent Proof: Parent Proof: 0xf00baa… 0xd00d1e… 0xc0ffee… 0xf00baa… TX: Alice -> Bob TX: Mallory -> Bob TX: Ted -> Alice TX: Mallory -> Alice The University of Sydney Page 2

Blockchain Block #41 Block #42 Block #43 Block #44 Proof: Proof: Proof: Proof: 0xd00d1e… 0xc0ffee… 0xf00baa… 0xfabfab… Parent Proof: Parent Proof: Parent Proof: Parent Proof: 0xf00baa… 0xd00d1e… 0xc0ffee… 0xf00baa… TX: Alice -> Bob TX: Mallory -> Bob TX: Ted -> Alice TX: Mallory -> Alice The University of Sydney Page 3

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$ 10 The University of Sydney Page 6

$ 10 The University of Sydney Page 7

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$ 10 $ 10 The University of Sydney Page 10

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What da h… $ 10 The University of Sydney Page 13

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Q: is it possible to double spend on Ethereum with network attacks? The University of Sydney Page 15

Approaches to study … – Goals: 1. How the blockchain system decide a block? 2. How the blockchain system resolve fork? The University of Sydney Page 16

Approaches to study … – Goals: 1. How the blockchain system decide a block? 2. How the blockchain system resolve fork? – Reading the documentation – Scattered and un-organised information: website, wiki, github, issue tracker, yellow paper , etc. – Lack of necessary information – Intention ≠ Actual implementation – Reading the code !! – Running it for real because the devil is in the detail … The University of Sydney Page 17

Decided Blocks and Committed Transactions in PoW/Ethereum – Given a blockchain with parameter k, a block at index i is decided when the chain depth reaches i+k – A transaction is committed if it belongs to a decided block i i+1 0 1 i+k-1 i+k Decided Undecided Transaction block block The University of Sydney Page 18 Ekparinya et al, "Impact of Man-in-the-middle Attacks on Ethereum"

Expected Branch Selection in PoW/Ethereum: GHOST The University of Sydney Page 19

Expected Branch Selection in PoW/Ethereum: GHOST The University of Sydney Page 20

Actual Branch Selection in PoW/Ethereum: Highest total difficulty The University of Sydney Page 21

Actual Branch Selection in PoW/Ethereum: Highest total difficulty The University of Sydney Page 22

Example 1: Man-in-the-middle Attack against PoW The University of Sydney Page 23

Example 1: Man-in-the-middle Attack against PoW The University of Sydney Page 24

Example 1: Man-in-the-middle Attack against PoW The University of Sydney Page 25

Example 1: Man-in-the-middle Attack against PoW The University of Sydney Page 26

Example 1: Man-in-the-middle Attack against PoW The University of Sydney Page 27

Decided Blocks and Committed Transactions in AuRa PoA/Ethereum – A decision requires strictly more than half, only one partition may decide blocks Can decide a block The University of Sydney Page 31

Branch Selection in AuRa PoA/Ethereum : Longest branch The University of Sydney Page 32

Branch Selection in AuRa PoA/Ethereum : Longest branch The University of Sydney Page 33

Example 2: The Cloning Attack against PoA The University of Sydney Page 34

Example 2: The Cloning Attack against PoA The University of Sydney Page 35

Example 2: The Cloning Attack against PoA The University of Sydney Page 36

Example 2: The Cloning Attack against PoA The University of Sydney Page 37

Example 2: The Cloning Attack against PoA The University of Sydney Page 38

The requirements for the experiments – Control over computing resources ➢ OpenStack Private Cloud – Network control and isolation ➢ Virtual switches, Virtual routers (Quagga) and VLAN – Highly automated ➢ OpenStack API and Ethereum API – Robust data collection ➢ Elasticsearch The University of Sydney Page 39

Testbed Provisioning The University of Sydney Page 40

Testbed Provisioning The University of Sydney Page 41

Testbed Provisioning The University of Sydney Page 42

Testbed Provisioning The University of Sydney Page 43

Time for Discussions !! The University of Sydney Page 44