[PPT] - SECMACE: Scalable and Robust Identity and Credential Management PowerPoint Presentation

SLIDE 1

KTH ROYAL INSTITUTE OF TECHNOLOGY

SECMACE: Scalable and Robust Identity and Credential Management Infrastructure in Vehicular Communication Systems

M. Khodaei, H. Jin and P

. Papadimitratos

Networked Systems Security Group (NSS) In IEEE Transactions on Intelligent Transportation Systems (April 2018)

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Outline Secure Vehicular Communication (VC) Systems Problem Statement System Model Security and Privacy Analysis Performance Evaluation Summary of Contributions and Future Steps

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SLIDE 3

Vehicular Communication (VC) Systems

Figure: Photo Courtesy of the Car2Car Communication Consortium (C2C-CC) 3/42

SLIDE 4

Security and Privacy for VC Systems1

Basic Requirements

◮ Message authentication & integrity ◮ Message non-repudiation ◮ Access control ◮ Entity authentication ◮ Accountability ◮ Privacy protection

Vehicular Public-Key Infrastructure (VPKI)

◮ Pseudonymous authentication ◮ Trusted Third Party (TTP):

◮ Certification Authority (CA) ◮ Issues credentials & binds users to their pseudonyms 1P . Papadimitratos, et al. “Securing Vehicular Communications - Assumptions, Require- ments, and Principles,” in ESCAR, Berlin, Germany, pp. 5-14, Nov. 2006. P . Papadimitratos, et al. “Secure Vehicular Communication Systems: Design and Architec- ture,” in IEEE Communications Magazine, vol. 46, no. 11, pp. 100-109, Nov. 2008.

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SLIDE 5

Security and Privacy for VC Systems (cont’d)

◮ Sign packets with the private key, corresponding to the current

valid pseudonym

◮ Verify packets with the valid pseudonym ◮ Cryptographic operations in a Hardware Security Module (HSM)

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SLIDE 6

State-of-the-art Standardization and harmonization efforts

◮ IEEE 1609.2 [1], ETSI [2] and C2C-CC [3] ◮ VC related specifications for security and

privacy-preserving architectures Projects

◮ SEVECOM, EVITA, PRECIOSA, OVERSEE,

DRIVE-C2X, Safety Pilot, PRESERVE, CAMP-VSC3 Proposals

◮ V-Token, CoPRA, SCMS , SEROSA, PUCA

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SLIDE 7

Outline Secure Vehicular Communication (VC) Systems Problem Statement System Model Security and Privacy Analysis Performance Evaluation Summary of Contributions and Future Steps

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SLIDE 8

Problem Statement and Motivation The design of a VPKI

◮ Resilience ◮ Stronger adversarial model (than fully-trustworthy entities)

◮ User privacy protection against “honest-but-curious” entities ◮ User privacy enhancement and service unlinkability

(inference of service provider or time)

◮ Pseudonym acquistion policies

◮ How should each vehicle interact with the VPKI, e.g., how

frequently and for how long?

◮ Should each vehicle itself determine the pseudonym

lifetime?

◮ Operation across multiple domains, thus a scalable design ◮ Efficiency and robustness

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SLIDE 9

Security and Privacy Requirements for the VPKI Protocols

◮ Authentication, communication integrity and confidentiality ◮ Authorization and access control ◮ Non-repudiation, accountability and eviction (revocation) ◮ Privacy

◮ Anonymity (conditional) ◮ Unlinkability

◮ Thwarting Sybil-based misbehavior ◮ Availability

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SLIDE 10

Adversarial Model External adversaries Internal adversaries Stronger adversarial model

Protection against honest-but-curious VPKI entities

◮ Correct execution of protocols but motivated to profile users ◮ Concealing pseudonym provider identity and acquisition time, and

reducing pseudonyms linkability (inference based on time)

Multiple VPKI entities could collude 10/42

SLIDE 11

Outline Secure Vehicular Communication (VC) Systems Problem Statement System Model Security and Privacy Analysis Performance Evaluation Summary of Contributions and Future Steps

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SLIDE 12

Secure VC System

◮

Root Certification Authority (RCA)

◮

Long Term CA (LTCA)

◮

Pseudonym CA (PCA)

◮

Resolution Authority (RA)

◮

Lightweight Directory Access Protocol (LDAP)

◮

Roadside Unit (RSU)

◮

Trust established with RCA, or through cross certification

RSU 3/4/5G

PCA LTCA PCA LTCA RCA PCA LTCA B A A certifies B Cross-certification Communication link Domain A Domain B Domain C RA RA RA B

X-Cetify

LDAP LDAP Message dissemination {Msg}(Piv),{Pi

v}(PCA)

{Msg}(Piv),{Pi

v}(PCA)

Figure: VPKI Overview 12/42

SLIDE 13

System Model

F-LTCA PCA H-LTCA RCA B A A certifies B Communication link Home Domain (A) Foreign Domain (B) LDAP PCA RA RA

1. LTC
2. n-tkt
I. f-tkt req.
II. f-tkt III. n-tkt
3. psnym req.
4. psnyms acquisition
IV. psnym req.
V. psnyms acquisition

Figure: VPKI Architecture 13/42

SLIDE 14

Pseudonym Acquisition Policies

User-controlled policy (P1) Oblivious policy (P2) Universally fixed policy (P3) ΓP3 ΓP3 ΓP3 System Time

Trip Duration

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

ΓP2 ΓP2

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

}

τP

Unused Pseudonyms

tstart

Expired Pseudonym

tend

◮ P1 & P2: Requests could act as user “fingerprints”; the exact time

f requests and all subsequent requests until the end of trip could

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SLIDE 15

Vehicle Registration and Long Term Certificate (LTC) Update

V H-LT CA

1. LKv, Lkv
2. (LKv)σLkv , N, t
3. Cert(LT Cltca, LKv)
4. LT Cv, N + 1, t

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SLIDE 16

Ticket Acquisition Protocols

Protocol 1 Ticket Request (from the LTCA)

1: procedure REQTICKET(Px, ΓPx, ts, te, tdate) 2:

if Px = P1 then

3:

(ts, te) ← (ts, te)

4:

else if Px = P2 then

5:

(ts, te) ← (ts, ts + ΓP2)

6:

else if Px = P3 then

7:

(ts, te) ← (tdate + Γi

P3), tdate + Γi+1 P3 )

8:

end if

9:

ζ ← (Idtkt-req, H(IdPCARndtkt), ts, te)

10:

(ζ)σv ← Sign(Lkv, ζ)

11:

return ((ζ)σv , LTCv, N, tnow)

12: end procedure

◮

Run over Transport Layer Security (TLS) with mutual authentication

Protocol 2 Issuing a Ticket (by the LTCA)

1: procedure ISSUETICKET((msg)σv , LTCv, N, tnow) 2:

Verify(LTCv, (msg)σv )

3:

IKtkt ← H(LTCv||ts||te||RndIKtkt)

4:

ζ ← (SN, H(IdPCARndtkt), IKtkt, RndIKtkt, ts, te, Exptkt)

5:

(tkt)σltca ← Sign(Lkltca, ζ)

6:

return ((tkt)σltca, N + 1, tnow)

7: end procedure

◮

“ticket identifiable key” (IKtkt) binds a ticket to the corresponding LTC

◮

Preventing a compromised LTCA from mapping a different LTC during resolution process

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SLIDE 17

Pseudonyms Acquisition Protocols

Protocol 3 Pseudonym Request (from the PCA)

1: procedure REQPSNYMS(ts, te, (tkt)σltca) 2:

for i:=1 to n do

3:

Begin

4:

Generate(K i

v, ki v)

5:

(K i

v)σki

v ← Sign(ki

v, K i v)

6:

End

7:

psnymReq ← (Idreq, Rndtkt, ts, te, (tkt)σltca, {(K 1

v )σk1

v , ..., (K n

v )σkn

v }, N, tnow)

8:

return psnymReq

9: end procedure

◮

Run over TLS with unidirectional (server-only) authentication

Protocol 4 Issuing Pseudonyms (by the PCA)

1: procedure ISSUEPSNYMS(psnymReq) 2:

psnymReq → (Idreq, Rndtkt, ts, te, (tkt)σltca, {(K 1

v )σk1

v , ..., (K n

v )σkn

v }, N, tnow)

3:

Verify(LTCltca, (tkt)σltca)

4:

H(Idthis-PCARndtkt) ? = H(IdPCARndtkt)

5:

[ts, te] ? = ([ts, te])tkt

6:

for i:=1 to n do

7:

Begin

8:

Verify(K i

v, (K i v)σki

v )

9:

IKPi ← H(IKtkt||K i

v||ti s||ti e||RndIK i

v)

10:

ζ ← (SNi, K i

v, IKPi, RndIK i

v , ti

s, ti e)

11:

(Pi

v)σpca ← Sign(Lkpca, ζ)

12:

End

13:

return ({(P1

v )σpca, . . . , (Pn v )σpca}, N+1, tnow)

14: end procedure

◮

“pseudonym identifiable key” (IKPi ) binds a pseudonym to the corresponding ticket

◮

Preventing a compromised PCA from mapping a different ticket during resolution process

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SLIDE 18

Ticket and Pseudonym Acquisition

V H-LTCA PCA

1. H(PCAID Rnd256), ts, te, LT Cv, N, t
2. Cert(LT Cltca, tkt)
3. tkt, N + 1, t
4. tkt, Rnd256, ts′, te′, {(K1

v)σk1

v , ..., (Kn

v )σkn

v }, N ′, t

5. Cert(LT Cpca, P i

v)

6. {P 1

v , . . . , P n v }, N ′ + 1, t

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SLIDE 19

Roaming User: Foreign Ticket Authentication

V LDAP H-LT CA

1. LDAP Req.

2.LDAP Search

3. LDAP Res.
4. H(F-LT CAID Rnd256), ts, te, LT Cv, N, t
5. Cert(LT Cltca, f-tkt)
6. f-tkt, N + 1, t

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SLIDE 20

Native Ticket and Pseudonym Acquisition in the Foreign Domain

V F-LT CA PCA

1. f-tkt, H(PCAID||Rnd′

256), Rnd256, N, t

2.Cert(LT Cltca, n-tkt)

3. n-tkt, N + 1, t
4. n-tkt, Rnd′

256, ts′, te′, {(K1 v)σk1

v , ..., (Kn

v )σkn

v }, N ′, t

5. Cert(LT Cpca, P i

v)

6. {P 1

v , . . . , P n v }, N ′ + 1, t

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SLIDE 21

Pseudonym Revocation and Resolution

RA PCA LT CA

1. Pi, N, t

2.Update CRL

3. tkt, N + 1, t

4.SNtkt, N ′, t 5.Resolve LT Cv 6.LT Cv, N ′ + 1, t

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SLIDE 22

Outline Secure Vehicular Communication (VC) Systems Problem Statement System Model Security and Privacy Analysis Performance Evaluation Summary of Contributions and Future Steps

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SLIDE 23

Security and Privacy Analysis

◮ Communication integrity, confidentiality, and non-repudiation

◮ Certificates, TLS and digital signatures

◮ Authentication, authorization and access control

◮ LTCA is the policy decision and enforcement point ◮ PCA grants the service ◮ Security association discovery through LDAP

◮ Concealing PCAs, F-LTCA, actual pseudonym acquisition period

◮ Sending H(PCAid Rnd256), ts, te, LTCv to the H-LTCA ◮ PCA verifies if [t′ s, t′ e] ⊆ [ts, te]

◮ Thwarting Sybil-based misbehavior

◮ LTCA never issues valid tickets with overlapping lifetime (for a given

domain)

◮ A ticket is bound to a specific PCA ◮ PCA keeps records of ticket usage

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SLIDE 24

Linkability based

n

Timing Information

f Credentials

5 10 15 20 25 30 35 40 45 50 55 60 System Time [min.] 1 2 3 4 5 6 7 8 9 10

τP= 5 min.

5 10 15 20 25 30 35 40 45 50 55 60 System Time [min.] 1 2 3 4 5 6 7 8 9 10

τP= 5 min., ΓP2= 15min.

5 10 15 20 25 30 35 40 45 50 55 60 System Time [min.] 1 2 3 4 5 6 7 8 9 10

τP= 5 min., ΓP3= 15min.

(a) P1: User-controlled policy (b) P2: Oblivious policy (c) P3: Universally fixed policy

◮ Non-overlapping pseudonym lifetimes from eavesdroppers’ perspective ◮ P1 & P2: Distinct lifetimes per vehicle make linkability easier (requests/pseudonyms could act as user ‘fingerprints’) ◮ P3: Uniform pseudonym lifetime results in no distinction

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SLIDE 25

Outline Secure Vehicular Communication (VC) Systems Problem Statement System Model Security and Privacy Analysis Performance Evaluation Summary of Contributions and Future Steps

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SLIDE 26

Experimental Setup

◮ VPKI testbed

◮ Implementation in C++ ◮ OpenSSL: TLS and Elliptic Curve Digital Signature Algorithm (ECDSA)-256 according to the standard [1]

◮ Network connectivity

◮ Varies depending on the actual OBU-VPKI connectivity ◮ Reliable connectivity to the VPKI (e.g., RSU, Cellular, opportunistic WiFi)

Table: Servers and Clients Specifications

LTCA PCA RA Clients VM Number 2 5 1 25 Dual-core CPU (Ghz) 2.0 2.0 2.0 2.0 BogoMips 4000 4000 4000 4000 Memory 2GB 2GB 1GB 1GB Database MySQL MySQL MySQL MySQL Web Server Apache Apache Apache

Load Balancer

Apache Apache

Emulated Threads
400

◮ Use cases

◮ Pseudonym provision ◮ Performing a DDoS attack

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SLIDE 27

Experimental Setup (cont’d)

Table: Mobility Traces Information

TAPASCologne LuST [5] Number of vehicles 75,576 138,259 Number of trips 75,576 287,939 Duration of snapshot (hour) 24 24 Available duration of snapshot (hour) 2 (6-8 AM) 24 Average trip duration (sec.) 590.49 692.81 Total trip duration (sec.) 44,655,579 102,766,924

◮ Main metric

◮ End-to-end pseudonym

acquisition latency from the initialization of ticket acquisition protocol till successful completion of pseudonym acquisition protocol

Table: Servers & Clients Specifications

LTCA PCA Client Number of entities 1 1 1 Dual-core CPU (Ghz) 2.0 2.0 2.0 BogoMips 4000 4000 4000 Memory 2GB 2GB 1GB Database MySQL MySQL MySQL

◮ N.B. PRESERVE Nexcom boxes specs: dual-core 1.66 GHz, 2GB Memory

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SLIDE 28

End-to-end Latency for P1, P2, and P3

Choice of parameters: ◮ Frequency of interaction and volume

f workload to a PCA

◮ Γ=5 min., τP=0.5 min., 5 min. LuST dataset (τP = 0.5 min): ◮ P1: Fx(t = 167 ms) = 0.99 ◮ P2: Fx(t = 80 ms) = 0.99 ◮ P3: Fx(t = 74 ms) = 0.99

(P1) (P2) (P3)

TAPASCologne dataset LuST dataset

20 40 60 80 100 120

System Time [min.]

20 40 60 80 100 120 140

End-to-End Latency [ms] User-controlled Policy (P1): 1 LTCA and 1 PCA

τP= 0.5 min. τP= 5 min.

200 400 600 800 1000 1200 1400

System Time [min.]

20 40 60 80 100 120 140

End-to-End Latency [ms] User-controlled Policy (P1): 1 LTCA and 1 PCA

τP= 0.5 min. τP= 5 min.

20 40 60 80 100 120

System Time [min.]

20 40 60 80 100 120 140

End-to-End Latency [ms] Oblivious Policy (P2): 1 LTCA and 1 PCA

τP= 0.5 min. τP= 5 min.

200 400 600 800 1000 1200 1400

System Time [min.]

20 40 60 80 100 120 140

End-to-End Latency [ms] Oblivious Policy (P2): 1 LTCA and 1 PCA

τP= 0.5 min. τP= 5 min.

20 40 60 80 100 120

System Time [min.]

20 40 60 80 100 120 140

End-to-End Latency [ms] Universally Fixed Policy (P3): 1 LTCA and 1 PCA

τP= 0.5 min. τP= 5 min.

200 400 600 800 1000 1200 1400

System Time [min.]

20 40 60 80 100 120 140

End-to-End Latency [ms] Universally Fixed Policy (P3): 1 LTCA and 1 PCA

τP= 0.5 min. τP= 5 min.

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SLIDE 29

Latency Comparison for Different Policies

1 2 3 4 5 6 7 8 9 10

Pseudonym Lifetime [min.]

10 20 30 40 50 60 70 80

Average End-to-End Latency [ms]

Average End-to-End Latency Comparison of P1, P2 and P3

P1 P2 (ΓP2= 10 min.) P3 (ΓP3= 10 min.)

Figure: End-to-end latency comparison for different policies (Tapas Dataset) 29/42

SLIDE 30

Pseudonym Utilization, LuST Dataset for P2 & P3

200 400 600 800 1000 1200

Pseudonym Lifetime [sec.]

5 10 15 20

Average Number of Unused Pseudonyms Pseudonym Utilization with Oblivious Policy (P2)

ΓP2= 5 min. ΓP2= 10 min. ΓP2= 15 min. ΓP2= 20 min.

200 400 600 800 1000 1200

Pseudonym Lifetime [sec.]

5 10 15 20

Average Number of Unused Pseudonyms Pseudonym Utilization with Universally Fixed Policy (P3)

ΓP3= 5 min. ΓP3= 10 min. ΓP3= 15 min. ΓP3= 20 min. P2: Oblivious Policy P3: Universally Fixed Policy

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SLIDE 31

The VPKI Servers under a DDoS Attack

200 400 600 800 1000 Faked Requests [per sec.] 50 100 150 200 250 300 350 400 Overhead [ms]

The VPKI Servers under a DDoS Attack: 1 LTCA and 1 PCA

No countermeasure With countermeasure (L=5)

Figure: Overhead to obtain pseudonyms, LuST dataset with P1 (τP = 5 min.) 31/42

SLIDE 32

Performance Evaluation for Ticket and Pseudonym Acquisition

50 100 150 200 250 300

Processing Delay [ms]

0.00 0.20 0.40 0.60 0.80 0.95 1.00

Cumulative Probability LTCA Server Performance: LuST Dataset

1 2 3 4 0.00 0.20 0.40 0.60 0.80 0.95

50 100 150 200

Processing Delay [ms]

0.0 0.2 0.4 0.6 0.8 1.0

Cumulative Probability PCA Server Performance: LuST Dataset

τP= 1 min τP= 3 min τP= 5 min 10 20 30 40 50 0.00 0.20 0.40 0.60 0.80 0.95 Obtaining a Certificate Revocation List (CRL) Online Certificate Status Protocol (OCSP) validation

◮ Ticket Acquisition: Fx(t=4ms)=0.95 or Pr{t≤4ms}=0.95. ◮ Pseudonym Acquisition: Fx(t=52ms)=0.95 or

Pr{t≤52}=0.95. 32/42

SLIDE 33

Performance Evaluation for Pseudonym Revoca- tion (CRL or OCSP)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

End-to-End Latency [sec.]

0.00 0.20 0.40 0.60 0.80 0.95 1.00

Cumulative Probability Obtaining CRL from a PCA: LuST dataset

10K revoked pseudonyms 25K revoked pseudonyms 50K revoked pseudonyms 100K revoked pseudonyms

200 400 600 800 1000 1200 1400

System Time [min.]

10 20 30 40 50 60 70 80

End-to-End Latency [ms] OCSP Validation with 1 PCA: LuST dataset

1 pseudonym per request 100 pseudonyms per request 500 pseudonyms per request Obtaining a CRL OCSP validation

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SLIDE 34

Entities Response Time to Resolve & Revoke a Pseudonym

0.01 0.05 0.1 0.5 1 5 Number of Pseudonyms in the PCA Database (×106)

50 100 150 200

End-to-End Latency [ms]

Resolution & Revocation in a Single Domain Client Side Operations All RA Operations All PCA Operations All LTCA Operations 0.01 0.05 0.1 0.5 1 5

Number of Pseudonyms in the PCA Database (×106)

50 100 150 200

End-to-End Latency [ms]

Resolution & Revocation Across Domains

Client Side Operations All RA Operations All PCA Operations All LTCA Operations All Cross Domain Operations

Single Domain Operation Across Domains Operation

◮ On average 100 ms to resolve & revoke a pseudonym

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SLIDE 35

Comparison with Other Implementations

Table: Latency for issuing 100 pseudonyms (without communication delay) DelayPCA CPUPCA VeSPA [6] 817 ms 3.4 GHz SEROSA [7] 650 ms 2.0 GHz PUCA [8] 1000 ms 2.53 GHz PRESERVE PKI (Fraunhofer SIT) [9] ≈ 4000 ms N/A C2C-CC PKI (ESCRYPT) [3] 393 ms N/A SECMACE 260 ms 2.0 GHz 35/42

SLIDE 36

Outline Secure Vehicular Communication (VC) Systems Problem Statement System Model Security and Privacy Analysis Performance Evaluation Summary of Contributions and Future Steps

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SLIDE 37

Summary of Contributions

1. Facilitating multi-domain operation
2. Offering increased user privacy protection

◮ Honest-but-curious system entities ◮ Eliminating pseudonym linking based on timing information

3. Eradication of Sybil-based misbehavior
4. Proposing multiple generally applicable pseudonym

acquisition policies

5. Detailed analysis of security and privacy protocols
6. Extensive experimental evaluation

◮ Efficiency, scalability, and robustness ◮ Achieving significant performance improvement ◮ Modest VMs can serve sizable areas or domain

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SLIDE 38

Future Steps VPKI enhancements

◮ Evaluation of the level of privacy, i.e., unlinkability, based on

the timing information of the pseudonyms for each policy

◮ Evaluation of actual networking latency, e.g., OBU-RSU ◮ Rigorous analysis of the security and privacy protocols

Efficient distribution of revocation information

◮ How to disseminate pseudonyms validity information

without interfering with vehicles operations? 38/42

SLIDE 39

Bibliography I

[1] “IEEE Standard for Wireless Access in Vehicular Environments - Security Services for Applications and Management Messages,” IEEE Std 1609.2-2016 (Revision of IEEE Std 1609.2-2013), Mar. 2016. [2]

T. ETSI, “ETSI TS 103 097 v1. 1.1-Intelligent Transport Systems (ITS); Security; Security Header and

Certificate Formats, Standard, TC ITS,” Apr. 2013. [3] Car-to-Car Communication Consortium (C2C-CC), June 2013. [Online]. Available: http://www.car-2-car.org/ [4]

W. Whyte, A. Weimerskirch, V. Kumar, and T. Hehn, “A Security Credential Management System for

V2V Communications,” in IEEE VNC, Boston, MA, pp. 1–8, Dec. 2013. [5]

L. Codeca, R. Frank, and T. Engel, “Luxembourg Sumo Traffic (LuST) Scenario: 24 Hours of Mobility

for Vehicular Networking Research,” in IEEE VNC, Kyoto, Japan, pp. 1–8, Dec. 2015.

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Bibliography II

[6]

N. Alexiou, M. Laganà, S. Gisdakis, M. Khodaei, and P

. Papadimitratos, “VeSPA: Vehicular Security and Privacy-preserving Architecture,” in Proceedings of the 2nd ACM workshop on Hot topics on wireless network security and privacy, Budapest, Hungary, pp. 19–24, Apr. 2013. [7]

S. Gisdakis, M. Laganà, T. Giannetsos, and P

. Papadimitratos, “SEROSA: SERvice Oriented Security Architecture for Vehicular Communications,” in IEEE VNC, Boston, MA, USA, Dec. 2013. [8]

D. Förster, H. Löhr, and F. Kargl, “PUCA: A Pseudonym Scheme with User-Controlled Anonymity for

Vehicular Ad-Hoc Networks (VANET),” in IEEE VNC, Paderborn, Germany, Dec. 2014. [9] “Preparing Secure Vehicle-to-X Communication Systems - PRESERVE.” [Online]. Available: http://www.preserve-project.eu/ [10]

M. Khodaei, “Secure Vehicular Communication Systems: Design and Implementation of a Vehicular

PKI (VPKI),” Master’s thesis, Lab of Communication Networks (LCN), KTH University, Oct. 2012.

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SLIDE 41

Bibliography III

[11]

M. Khodaei, H. Jin, and P

. Papadimitratos, “Towards Deploying a Scalable & Robust Vehicular Identity and Credential Management Infrastructure,” in IEEE Vehicular Networking Conference (VNC), Paderborn, Germany, pp. 33–40, Dec. 2014. [12]

M. Khodaei and P

. Papadimitratos, “The Key to Intelligent Transportation: Identity and Credential Management in Vehicular Communication Systems,” IEEE VT Magazine, vol. 10, no. 4, pp. 63–69,

Dec. 2015.

[13] ——, “Evaluating On-demand Pseudonym Acquisition Policies in Vehicular Communication Systems,” in Proceedings of the First International Workshop on Internet of Vehicles and Vehicles of Internet, Paderborn, Germany, pp. 7–12, July 2016.

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SLIDE 42

SECMACE: Scalable and Robust Identity and Credential Management Infrastructure in Vehicular Communication Systems

M. Khodaei, H.Jin, and P