An Efficient and Spontaneous Privacy-Preserving Protocol for Secure Vehicular Communications Hu Xiong, Konstantin Beznosov, Zhiguang Qin, Matei Ripeanu presented by Jiaqi Gui Networked Systems Laboratory Electrical and Computer Engineering Department

An Efficient and Spontaneous Privacy-Preserving 2  Life-critical  alerting and monitoring functionality during intersection crossing, lane merging, etc.  Value-added  enhancing drivers’ traveling experience by providing convenient Internet access, navigation, toll payment services, etc. 2 Types of Applications

An Efficient and Spontaneous Privacy-Preserving 3  Life-critical  alerting and monitoring functionality during intersection crossing, lane merging, etc. Security is critical!  Think of the damage a malicious attack could do  Value-added  enhancing drivers’ traveling experience by providing convenient Internet access, navigation, toll payment services, etc. 3 Types of Applications

An Efficient and Spontaneous Privacy-Preserving 4  Life-critical  alerting and monitoring functionality during intersection crossing, lane merging, etc. Security is critical!  Think of the damage a malicious attack could do  Value-added  enhancing drivers’ traveling experience by providing convenient Internet access, navigation, toll payment services, etc. 4 Types of Applications

An Efficient and Spontaneous Privacy-Preserving 5  Wireless communication devices installed on vehicles (On-Board Units - OBUs)  Road-side access points (RSUs)  Transportation Regulation Center (TRC) 5 Structure of Proposed Infrastructure for Vehicular Networks Vehicular networks

An Efficient and Spontaneous Privacy-Preserving 6  Conditional privacy preservation  Spontaneous  Efficient Security Requirements for a Vehicular Communication Protocol

An Efficient and Spontaneous Privacy-Preserving 7  Conditional privacy preservation The identity of vehicles should be protected However, incident investigation may require revealing identities of participating vehicles  Offline  Only by authorized parties  Spontaneous  Efficient Security Requirements …

An Efficient and Spontaneous Privacy-Preserving 8  Conditional privacy preservation  Spontaneous Protocol should not require communication between cooperating vehicles in the critical path before sending each new message Protocol should not require support from the RSUs  RSUs may not cover all road segments at least in the initial deployment stages,  Efficient Security Requirements …

An Efficient and Spontaneous Privacy-Preserving 9  Conditional privacy preservation  Spontaneous  Efficient Low communication overheads Low storage overhead  Should not rely on  a large storage space at each vehicle, or  updating the group public key and private key at all unrevoked vehicles in case of a growing revocation list Low computational requirements Security Requirements …

An Efficient and Spontaneous Privacy-Preserving 10 Existing/Proposed Solutions SpontaeousEfficiency Storage Overhead Verification Overh. Solutions using a large numbers of anonymous keys (LAB) YesHighLow Solutions based on pure group signature (GSB) YesLowHigh Solutions based on using the roadside infrastructure (RSUB) No (RSU aided) Low Proposed solution (based on revocable ring signature) YesLow [LAB] M. Raya, J. P. Hubaux, Securing Vehicular Ad Hoc Networks, Journal of Computer Security, 15(1), [GSB] X. Lin et al., GSIS: A Secure and Privacy-Preserving Protocol for Vehicular Communications, IEEE Trans on Vehicular Technology, 56(6), [RSUB] R. Lu et al., ECPP: Efficient Conditional Privacy Preservation Protocol for Secure Vehicular Communications, INFOCOM 2008 (Note: only solutions that provide conditional privacy are presented)

An Efficient and Spontaneous Privacy-Preserving 11  Introduction & Motivation  Past Solutions  The Proposed Solution  Analysis  Conclusions Outline

An Efficient and Spontaneous Privacy-Preserving 12 Key Ingredients Public/private keys. Ring signature [Rivest et al. 2001]  Provides: Anonymity: attacker can not infer which member of a group has signed. Spontaneity: any member of a group can sign without additional setup Revocable ring signature [Liu et al. 2007]  Provides conditional anonymity: an authority can reveal the identity of the real signer

An Efficient and Spontaneous Privacy-Preserving 13 Outline of the Proposed Solution Actual Message Signer Vehicle initialized with: Its own public/private key pair: (x i, y i ) The public key of TRC: y TRC Constants of the signature protocol

An Efficient and Spontaneous Privacy-Preserving 14 Outline of the Proposed Solution y1y1 y2y2 ynyn … Actual Message Signer Vehicles encountered in the past y k – public keys Vehicle initialized with: Its own public/private key pair: (x i, y i ) The public key of TRC: y TRC Constants of the signature protocol

An Efficient and Spontaneous Privacy-Preserving 15 Outline of the Proposed Solution y1y1 y2y2 ynyn … Actual Message Signer Vehicles encountered in the past Vehicle initialized with: Its own public/private key pair: (x i, y i ) The public key of TRC: y TRC Constants of the signature protocol Vehicle collects public keys of other vehicles encountered in the past

An Efficient and Spontaneous Privacy-Preserving 16 Outline of the Proposed Solution y1y1 y2y2 ynyn … Actual Message Signer Message Generation: (y 1 +y 2 +…+y n, M,y TRC,x i ) Vehicle generates the revocable ring signature using: Its own private key: x i A set of public keys of other N vehicles: y 1,y 2,…y n The public key of TRC: y TRC The message M Vehicles encountered in the past

An Efficient and Spontaneous Privacy-Preserving 17  Introduction & Motivation  Past Solutions  Outline of the Proposed Solution  Analysis  Conclusions Outline

An Efficient and Spontaneous Privacy-Preserving 18  Identity privacy preservation  Given a valid ring signature of a message, it is computationally difficult to identify the actual signer by any adversary  Property provided by ring signatures  Tracing to a real identity  Given the signature, the TRC who knows x TRC, can reveal the real identity of a message sender Conditional Privacy Preservation

An Efficient and Spontaneous Privacy-Preserving 19  Spontaneity  The vehicle can specify the ring (the set of vehicles) needed to generate the signature arbitrarily (i.e., without any new interaction with other vehicles or RSUs)  [Additional property] Multi-level privacy  Each vehicle can select the degree of privacy that fits its own requirements by choosing the number of public keys used in the message generation phase. Spontaneous and Multi-Level

An Efficient and Spontaneous Privacy-Preserving 20 Comparing Overheads to Existing/Proposed Solutions SpontaeousEfficiency Storage Overhead Verification Overh. Solutions using a large numbers of anonymous keys (LAB) YesHighLow Solutions based on pure group signature (GSB) YesLowHigh Solutions based on using the roadside infrastructure (RRUB) No (RSU aided) Low Proposed solution (RSUB) (based on revocable ring signature) YesLow [LAB] M. Raya, J. P. Hubaux, Securing Vehicular Ad Hoc Networks, Journal of Computer Security, 15(1), [GSB] X. Lin et al., GSIS: A Secure and Privacy-Preserving Protocol for Vehicular Communications, IEEE Trans on Vehicular Technology, 56(6), [RSUB] R. Lu et al., ECPP: Efficient Conditional Privacy Preservation Protocol for Secure Vehicular Communications, INFOCOM 2008 Hundreds or thousands of keys for each vehicle (all others schemes have one key pair per vehicle)

An Efficient and Spontaneous Privacy-Preserving 21 Comparing Overheads to Existing/Proposed Solutions SpontaeousEfficiency Storage Overhead Verification Overh. Solutions using a large numbers of anonymous keys (LAB) YesHighLow Solutions based on pure group signature (GSB) YesLow High Solutions based on using the roadside infrastructure (RRUB) No (RSU aided) Low Proposed solution (RSUB) (based on revocable ring signature) YesLow [LAB] M. Raya, J. P. Hubaux, Securing Vehicular Ad Hoc Networks, Journal of Computer Security, 15(1), [GSB] X. Lin et al., GSIS: A Secure and Privacy-Preserving Protocol for Vehicular Communications, IEEE Trans on Vehicular Technology, 56(6), [RSUB] R. Lu et al., ECPP: Efficient Conditional Privacy Preservation Protocol for Secure Vehicular Communications, INFOCOM 2008 Grows linearly with the number of revoked keys

An Efficient and Spontaneous Privacy-Preserving 22  Introduction  Motivation  The proposed Scheme  Analysis  Conclusion Outline

An Efficient and Spontaneous Privacy-Preserving 23 The proposed protocol provides  conditional privacy,  improves efficiency in terms of the number of keys stored at each vehicle, and complexity of sender authentication and verification.  does not require support from the roadside infrastructure  provides multi-level privacy Conclusions

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