1. TrustChain: A Sybil-resistant scalable blockchain
Source: Future Generation Computer Systems, Article in Press, Sep. 2017
Authors: Pim Otte, Martijn de Vos, and Johan Pouwelse
Speaker: Ren-Kai Yang
Date:2018/03/22

2. Outline Introduction Related works Proposed method Security analysis
Performance analysis
Conclusions

3. Introduction(1/3) Bitcoin Name Price Alice 50 Bob 60 David 1 Name
100
Bob 10
David 1
Bitcoin
Alice
Secret key [Alice → Bob, $50]
Secret key [Alice → Bob, $50]
David
Bob
Name
Price
Alice
100
Bob 10
David 1
Name
Price
Alice 50
Bob 60
David 1
Name
Price
Alice
100
Bob 10
David 1
Name
Price
Alice 50
Bob 60
David 1

4. Introduction(2/3) Transactions Header Global transaction broadcasts
"hash" : " b6b9a13b095e96db41c4a928b97ef2d944a9b31b2cc7bdc4",
"previousblockhash" : " a7bbd25a417c0374cc e8a9ca74442b01284f0569",
"difficulty" : ,
"time" : ,
"nonce" : ,
"merkleroot" : "c91c008c26e50763e9f548bb8b2fc323735f73577effbc55502c51eb4cc7cf2e",
"version" : 2,
"tx" : [ "d5ada064c6417ca25c4308bd158c34b77e1c0eca2a73cda16c737e7424afba2f", "b268b45c59b39d b9918caf0ba9d97c56f3b91956ff877c503fbe",
more transactions ... ],
"confirmations" : 35561,
"size" : ,
"height" : ,
"bits" : "1903a30c",
"chainwork" : " e92aaf53afa1a", "nextblockhash" : " c269dd6ed714dd5db39d36b d78dfd431ba7" }
Header
Transactions
Blockchain
Global transaction broadcasts
Proof-of-Work mechanisms
7 transactions per second
Prev Hash
Nonce
Prev Hash
Nonce
Prev Hash
Nonce
Merkle Root
Timestamp
Merkle Root
Timestamp
Merkle Root
Timestamp
Hash01
Hash23
Hash02
Hash03
Tx 02
Tx 03

5. Introduction(3/3)
Sybil attack in P2P network

6. Related works
Maximum flow B D 7
9+3=12 9 7 5 2 9 2 2 6 4 1 3 A C

7. Proposed method(1/4) – TrustChain architecture
Traditional blockchain
Hash C D F B
Hash A
Hash A
Hash A
Hash A
Hash B
Hash E
Hash G
Hash F C D
Hash F B

8. Proposed method(2/4) – TrustChain architectureB
Hash
Hash A
Hash A
Hash A
Hash E
Hash G
Hash F B D
Hash A
Hash C
Hash D
Hash B
Hash D
Hash F
Hash D

9. Proposed method(3/4) – Netflow accounting mechanism
9 + 3 = 12
6 + 3 = 9
Sp= 3
Cp= 3
Ct= 4
St= 2 2 p t 9 3 2 5 6 3 q r 4
Cq= -3
Sq= 0

10. Proposed method(4/4) – α-Netflow accounting mechanism
9 + 3 = 12
3 + 2 = 5
Sp= 7
Cp= 7
Ct= 4
St= 2 2 p t
α = 2 3 9 2 5 3 3 q r 2
Cq= 1
Sq= 1

11. Security analysis(1/3) Replay attack A B A A C B Hash Hash Hash Hash

12. Security analysis(2/3) Double spending attack A B A D A C A G Hash

13. Security analysis(3/3)
Sybil attack
sj1 5 i 2 j 5
sj2 5
sj3

14. Performance analysis(1/2)
1.6 transactions per second
18.1 transactions per second

15. Performance analysis(2/2)

16. Conclusions
Detection
Sybil attack