Secure Pub-Sub: Blockchain-based Fair Payment with Reputation for Reliable Cyber Physical Systems Source : IEEE Access, Vol. 6, pp. 12295-12303, Jan. 2018 Authors : Yanqi Zhao, Yong Yu, Yannan Li, Qilin Mu, Bo Yang Speaker : Fengyu Chiu Date : 2018/10/1

Outline Introduction Preliminaries Proposed scheme Potential attacks Security analysis Performance analysis Conclusions

Introduction Publisher Broker Subscriber Blockchain system Subscription Message Match

Preliminaries –smart contract(1/2) Coin Ice cream Store

Preliminaries – Reputation System(2/2) Explicit rating(D) Score: 0-1 Implicit rating(E) Positive activity Negative activity

Proposed scheme Event Make deposit and subscription Blockchain system Payment Topic Publisher Bitcoin and reputation Notification Subscriber Sensors Stream Sensors Stream

Proposed scheme - Setup Security parameters: k Public parameters Choose prime p,q (q|p-1) 𝑔∈ 𝐺 𝑞 Random value 𝑘← {0,1} 𝑘 𝐻 : {0,1} ∗ → 𝐺 𝑞 𝐻 1 : {0,1} 𝑘 → 𝐺 𝑞 Key pair(Pk,SK) 𝑆𝑖𝑔 𝑝 (𝑚)

Proposed scheme - Publish Reputation value: 𝐹 𝑅 Choose 𝑥∈ 𝑍 𝑞 Publisher Computes 𝑦= 𝑔 𝑥 Blockchain system 𝐹 𝑅 , 𝑦 , Topic Threshold: 𝜃 Value d’

Proposed scheme - Subscribe Compute 𝑤=𝐻(Topic) Choose 𝑟 0 ∈ 𝑍 𝑞 Subscriber Blockchain system F Compute 𝐹= {h, 𝑣 1 } ℎ= 𝑔 𝑟 0 , 𝑣 1 = 𝑦 𝑟 0 𝑤 Value b

Proposed scheme - Match Verify 𝐻 Topi c ′ = 𝑣 1 ℎ 𝑥 𝑘 1 ∈ {0,1} 𝑘 Publisher 𝑟 1 ∈ 𝑍 𝑞 Blockchain system F, D, L 𝑘 1 ′ = 𝐻 1 (𝑘, 𝑘 1 ) 𝑧 1 = 𝑔 𝑟 1 𝑧 2 = ℎ 𝑟 1 ∙ 𝑘 1 ′ Symmetric encryption 𝐶=𝐸𝑛𝑐( 𝑘 1 ,𝑀) D : { 𝑧 1 , 𝑧 2 ,𝐶} L = H(F)

Proposed scheme - Verification and Payment 𝐻 1 : {0,1} 𝑘 → 𝐺 𝑞 𝑘 𝑠 ′ = 𝐻 1 −1 𝑘, 𝑘 𝑠 = 𝐻 1 −1 𝑘, 𝑘 1 ′ = 𝑘 1 Verification 𝑘 𝑠 = 𝑧 2 𝑧 1 − 𝑟 0 = 𝑘 1 ′ 𝑘 𝑠 ′ = 𝐻 1 −1 𝑘, 𝑘 𝑠 𝑀=Dec( 𝑘 𝑠 ′ ,𝐶) Publisher Subscriber 𝐹 𝑅 , L, d’ Blockchain system 𝐹 𝑅 , L, d’ Payment 𝐹 𝑅 , L Value d’ Redeem Value b

Proposed scheme - Others Publisher Redeem value d’ Malicious subscriber Value b Malicious publisher Value d’

Potential attacks Denial of service attack(Dos attack) Unfair attack/Collusion attack Standard deviation Re−Entry attack IP address

Security analysis Confidentiality Symmetric encryption Completeness Fairness Anonymous

Performance analysis(1/2) [10] M. A. Tariq, B. Koldehofe, A. Altaweel, and K. Rothermel, “Providingbasic security mechanisms in broker-less publish/subscribe systems,” Proc. 4th ACM Int. Conf. Distrib. Event-Based Syst., pp. 3849, Jul. 2010. [8] Y. Baseri, B. Takhaei and J. Mohajeri, “Secure untraceable offline electronic cash system,” Scientia Iranica, 20(3), pp. 637–646, 2013. [11] M. A. Tariq, B. Koldehofe, and K. Rothermel, “Securing broker-less publish/subscribe systems using identity-based encryption,” IEEE Trans. Parallel Distrib. Syst., vol. 25, no. 2, pp. 518-528, Feb. 2014. [41] H. Huang, X. Chen, Q. Wu, X. Huang, and J. Shen, ``Bitcoin-based fair payments for outsourcing computations of fog devices,'' Future Generat. Comput. Syst., vol. 78, pp. 850-858, Jan. 2018. [Online]. Available: https://doi.org/10.1016/j.future.2016.12.016

Performance analysis(2/2) 123

Conclusions Fairness payment Confidentiality of data