Efficient Scheme for Secure and Privacy-Preserving Electric Vehicle Dynamic Charging System IEEE ICC 2017 Paris, France May 21 - 25, 2017 Presenter:
Outline I ntroduction Proposed Scheme Evaluations Conclusion
W hat is EV Dynam ic Charging? charging pads • The dynamic charging technology will enable Electric Vehicles (EVs) to charge their batteries while moving. • Charging pads are placed on the roads to charge the EVs through the magnetic induction. • Dynamic charging can can help the EVs that drive for long distances. 1
Problem Form ulation - The dynamic charging system should communicate with the EVs to only charge authorized vehicles and ensure payment integrity. Challenges: Authentication and secure payment • Security No entity should know the location of the drivers • Privacy • Efficiency Cost-effective pads have limited computational power • Scalability Large number of EVs and Pads. • Short contact tim e between the EVs and pads Our Objective To propose a scheme which can address all these challenges. 2
Outline Introduction Proposed Schem e Evaluations Conclusion
3 Netw ork Model
4 Exchanged Messages
1 . Anonym ous Coin Purchase ID i identity of the User TS Time stamp b e (g x ) blinded coin PBS(b e (g x ), date) Partial Blind Signature on coin g x , date, sig B (g x , date) Un-blinded Anonymous Coin 5
2 . Charging Request and paym ent EV i CSP Bank g x g y , E k (g y , g x ), 𝜏 C E k (g y , g x , date, Sig B (g x , date)) E k1 (g x , date, Sig B (g x , date)) Valid/Invalid Coin E k (Seed token) Steps 1 -3 : Key Establishment and Authentication Steps 4 -5 : Coin Verification Step 6 : Sending Token 6
3 . Efficient Hierarchical Authentication • EV should authenticate itself first to the CSP and then to RSU and then to charging pads. • In each level, the EV uses the secrets obtained from the previous level. 7
1 . Efficient Key Generation and Distribution: RSU 1 RSU 2 RSU nr RSU nr RSU 1 RSU 2 H( ) H( ) 𝜷 1,nr H( ) 𝜷 1,nr-1 H( ) 𝜸 1,nr 𝜸 1,nr-1 𝜷 1,1 𝜷 1,2 𝜸 1,2 𝜸 1,1 EV 1 EV 1 H k ( ) H k ( ) H( ) H( ) 𝜷 2,nr H( ) 𝜷 2,nr-1 𝜸 2,nr 𝜷 2,1 𝜷 2,2 𝜸 2,nr-1 H( ) 𝜸 2,1 𝜸 2,2 EV 2 EV 2 H k ( ) 𝜷 n-1,nr-1 H( ) 𝜷 n-1,nr 𝜷 n-1,1 𝜷 n-1,2 𝜸 n-1,nr 𝜸 n-1,nr-1 𝜸 n-1,1 H( ) H( ) 𝜸 n-1,2 EV n-1 EV n-1 H k ( ) H k ( ) H( ) H( ) 𝜷 n,nr-1 𝜷 n,1 𝜷 n,2 𝜷 n,nr H( ) 𝜸 n,nr-1 H( ) 𝜸 n,1 𝜸 n,2 EV n 𝜸 n,nr EV n Token Generation matrix-1 b/w CSP & RSUs Token Generation matrix-2 b/w CSP & RSUs • CSP shares a group secret key with all RSUs. • This key is used to distribute the seeds 𝛽 n,nr and β 1,1 for generating two token matrices. 8
Calculation of shared keys by RSUs: 𝜸 1,j 𝜷 1,j 𝜷 1,j ⊕ 𝜸 1,j 𝜸 2,j 𝜷 2,j 𝜷 2,j ⊕ 𝜸 2,j ⊕ 𝜸 n-1,j 𝜷 n-1,j 𝜷 n-1,j ⊕ 𝜸 n-1,j 𝜷 n,j 𝜸 n,j 𝜷 n,j ⊕ 𝜸 n,j • After computing its two sets of tokens, each RSU should compute the shared keys with the CSP by XORing corresponding two elements in the columns. 9
Calculation of shared keys betw een EV and RSU by an EV: • When an EV authenticates itself to the CSP, it received two seed tokens ( β i,1 and 𝛽 i,nr ) in the last step of charging request. • EV uses 𝛽 i,nr as seed for one hash chain β i,1 as seed for another hash chain • XORing corresponding two elements in two hash chains will give the shared keys. 10
Partial Charging: H( ) H( ) i,5 i,6 i,10 i,7 H( ) H( ) i,6 i,5 i,6 i,10 • One coin can be enough to charge from a certain number of pads. • Our scheme can be used to limit the number of RSUs’ pads an EV can charge from by limiting the number of keys the EV can calculate. 11
2 . Authentication at RSU and CP EV i RSU j Challenge: r i Response: H (α i,j ⊕ β i,j || r i ) Ack: H (α i,j ⊕ β i,j || r i || 1) • Challenge/response authentication to prove the knowledge of secret keys. • If the EV is authenticated by RSU, it sends a token to EV which will be used to compute the shared keys with the pads. • We use the same idea to authenticate EV at RSUs’ charging pads. 12
Outline Introduction Proposed Scheme Evaluations Conclusion
Evaluations • In order to evaluate the computation overhead, we used Crypto++ 5.6.2 library to measure the computation time of the cryptographic operations used in our scheme. • In our measurements, we used a 900MHz speed processor. Entities Storage Overhead Computation Overhead (n r � 20) + (n p � 20) 0.167 𝝂 sec + 0.125 𝝂 sec E.V bytes (n -1) � (n p -1) � 0.0418 𝝂 sec + Charging n � 20 bytes Pads 0.0418 𝝂 sec 2 � (n -1) � (n r -1) � 0.0418 𝝂 sec n � 20 bytes RSU + 0.23 𝝂 sec + 0.0418 𝝂 sec 2 � (n -1) � (n r -1) � 0.0418 𝝂 sec 2 � n � 20 bytes CSP + 0.23 𝝂 sec 13
Outline Introduction Proposed Scheme Evaluations Conclusion
• In this paper, we have proposed an efficient secure and privacy preserving scheme for Dynamic Charging System. • Proposed scheme can secure the prepaid payment while offering full anonymity to EV drivers. • Proposed an efficient technique to compute and share a large number of secret keys. • Developed an efficient hierarchical authentication scheme that uses efficient cryptosystems like hashing and Exclusive-OR operations. • Our measurements have demonstrated that the proposed scheme is efficient and scalable. 14
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