Security Approach for In-Vehicle Networking Using Blockchain Technology

Abstract

Security is nonnegotiable key point for in-vehicle networking. However, all communication between Electrical Control Unites (ECU) still suffer from security drawbacks like highly processing time or preserving confidentiality, integrity and authenticity. In this paper, we propose an approach to assess the feasibility of a private Blockchain technology to overcome the aforementioned drawbacks. In this approach, we consider in-vehicle networking contains two parts, namely, central (or connected) gateway (cGW) and switches. cGW and switches are Blockchain nodes, wherein Blockchain consensus protocols are what keep all the nodes on a network synchronized with each other. The approach considers any communication type between ECUs as an individual event, which can be a transaction, data entry or application execution. A use case of secure communication between two ECUs is presented as an evaluation mechanism for securing in-vehicle networking using the proposed Blockchain approach.

Full text

Security Approach for In-Vehicle Networking Using
Blockchain Technology
Maher Salem, Moayyad Mohammed, Ali Rodan
Higher Colleges of Technology
Department of Computer Information and Sciences
{msalem1,mmohammed,arodan}@hct.ac.ae
Abstract. Security is nonnegotiable key point for in-vehicle networking.
However, all communication between Electrical Control Unites (ECU) still
suffer from security drawbacks like highly processing time or preserving
confidentiality, integrity and authenticity. In this paper, we propose an approach
to assess the feasibility of a private Blockchain technology to overcome the
aforementioned drawbacks. In this approach, we consider in-vehicle networking
contains two parts, namely, central (or connected) gateway (cGW) and switches.
cGW and switches are Blockchain nodes, wherein Blockchain consensus
protocols are what keep all the nodes on a network synchronized with each other.
The approach considers any communication type between ECUs as an individual
event, which can be a transaction, data entry or application execution. A use case
of secure communication between two ECUs is presented as an evaluation
mechanism for securing in-vehicle networking using the proposed Blockchain
approach.
1 Introduction
Recent In-vehicle networking architecture includes ECUs, which are
intercommunicating with each other. All ECUs are attached to various buses like CAN,
CAN-FD, LIN, MOST, FlexRay [1]. The vehicle industry is expanding rapidly and
hence security becomes one of the major key point in vehicle communications.
Most of in-vehicle networking topology are now domain based architecture and each
domain contains all related ECUs attached to it. In addition, most of modern vehicles
have now the Ethernet as a new bus system. Ethernet is intended to connect inside the
vehicle high-speed communication requiring sub-systems like Advanced Driver
Assistant Systems (ADAS), navigation and positioning, multimedia, and connectivity
systems. For hybrid (HEVs) or electric vehicles (EVs), Ethernet will be a powerful part
of the communication architecture layer that enables the link between the vehicle
electronics and the Internet where the vehicle is a part of a typical Internet of Things
(IoT) application. Figure 1 shows the recent and most likely future in-vehicle
networking architecture [2].

Fig. 1. Overview of modern and future in-vehicle networking architecture
As seen in figure 1, all subnetworks with related ECUs are connected to the same
domain, which are connected to a cGW. All ECUs are communicating with each other
through the domain controllers and the cGW is managing all the communication
processes.
With the considered architecture in figure 1 and the communication to the external
resources using WiFi, Bluetooth or LTE, the vehicle becomes one of the complex and
complicated networks. This architecture allows more vulnerabilities to be emerged and
new attack vectors from the external networks to threaten the in-vehicle
communication. Moreover, the process of authentication and preserving the integrity
inside the vehicle network between all ECUs now needs more time for identity
verification from the controller and the cGW as well, which in turn is considered time
consuming. On the other hand, used cryptographic HW or SW solutions such as the
Trusted Platform Module (TPM), Hardware Secure Module (HSM), Software Guard
Extension (SGX), or Trusted Zone (TZ) is adding extra processing time, particularly
with asymmetric methods and each one is installed in different OEM vehicle
manufacturer, e.g. AUDI is implementing NXP HW solution from TPM or HSM while
BMW mostly SGX or TZ. This non de-facto security solution is also considered in time
processing issue [3].
There are currently several security approaches and architectures in the in-vehicle
networking to secure the data, prevent any unauthorized access, or to preserve the
integrity. All of these approaches are securing the vehicle but they still suffer from the
processing time and the lack to immutability. In the next section, some of the recent
security architecture will be discussed. In this article, we adopt the Blockchain
technology and propose an approach to overcome the previous shortages and strengthen
security and privacy inside the vehicle networks.
The Blockchain is defined as an open ledger that offers decentralization to the
parties. In addition, it also offers transparency, immutability, and security. It has many
features including being open, distributed, ledger, P2P and permanent. The function of

a Blockchain is straightforward. As it is a peer-to-peer network, a user needs to start a
transaction. Once done, a block is allocated to the said transaction. The transaction
block is also broadcasted to the network, and all the nodes in the network get the said
information. The block is then mined and validated. It is also added to the chain,
followed by a successful transaction. [4].
Blockchain is managed distributedly by a peer to peer network. Each node is
identified using a Public Key (PK). All communications between nodes, known as
transactions, are encrypted using PKs and broadcast to the entire network. Every node
can verify a transaction, by validating the signature of the transaction generator against
their PK. This ensures that Blockchain can achieve trustless consensus, meaning that
an agreement between nodes can be achieved without a central trust broker, e.g.
Certificate Authority (CA). A node will periodically collect multiple transactions from
its pool of pending transactions to form a block, which is broadcasted to the entire
network. The block is appended to the local copy of the Blockchain stored at a node if
all constituent transactions are valid. A consensus algorithm such as Proof of Work
(PoW) is employed to control which nodes can participate in the Blockchain. Once a
block is appended, it (or the constituent transactions) cannot be modified, since the hash
of each block is contained in the subsequent block in the chain, which ensures
immutability. A node can change its PK (i.e. identity) after each transaction to ensure
anonymity and privacy [5].
Consensus algorithms are a decision-making process for a group, where individuals
of the group construct and support the decision that works best for the rest of them. It’s
a form of resolution where individuals need to support the majority decision, whether
they liked it or not [4]. List of All Consensus Algorithms
 Proof-of-Work
 Proof-of-Stake
 Delegated Proof-of-Stake
 Leased Proof-Of-Stake
 Proof of Elapsed Time
 Practical Byzantine Fault Tolerance
 Simplified Byzantine Fault Tolerance
 Delegated Byzantine Fault Tolerance
 Directed Acyclic Graphs
 Proof-of-Activity
 Proof-of-Importance
 Proof-of-Capacity
 Proof-of-Burn
 Proof-of-Weight
Regarding the network between nodes, there are three types of network, namely
decentralized, centralized and distributed. Since in-vehicle networking ECUs are
related to one domain and all are controlled by the cGW, we adopted the centralized
network approach where all the nodes come under a single authority.
The rest of this article is divided as follows, section 2 discusses some related work
regarding in-vehicle security and Blockchain. Section3 presents our approach by
deploying Blockchain technology. Secure communication mechanism using the

proposed Blockchain will be presented in section 4. Finally, Discussion and conclusion
are presented in section 5.
2 Related Work
Cybersecurity in vehicle communication attracts researcher to propose and implement
a security solution to protect vehicle internal and external communication. However,
till now security still a major issue in vehicle communications. Rajbahadur et al.
conducted a survey about anomaly detection techniques in vehicle communication
using 3 dimensions with several subcategories. The main result was that most of prior
research evaluated their methods from simulations. proposed techniques ignored safety
of the vehicles while focusing on cybersecurity [6]. IOActive published a white paper
about the vulnerabilities in automotive industry and they concluded that vulnerabilities
have decreased in both impact and likelihood. In addition, they showed that most
common attack vectors are internal software components and network-connected
applications [7]. Li et al. presented also some explanation and declaration about
considering attacks and improving security in the connected vehicle cloud computing.
They have discussed and investigated all articles in the journal and give a professional
insight regarding cybersecurity and the attacks against vehicle networks [8].
M. Singh and S. Kim have discussed the challenges of automotive security in hardware
and software, and propose a security architecture for automotive security and also
mention future research challenges in automotive cyber security [9]. They have defined
possible future security issues related to intelligent vehicles such as secure
communication and secure routing. This article supports our approach by emphasizing
on the need for a novel security approach to protect vehicle communications.
Even pioneers in the automotive industry like NXP reviewed todays’ ECUs, especially
from a semiconductor technology perspective. After that they reviewed it regarding the
potential of future vehicle networks, it has described future ECUs along with the
limitations and opportunities. They have concluded that the domain based architectures
will be introduced on the short- to mid-term while for the central computing platform
items like safety, reliability and cost still need to be answered especially for the central
Module [10]. On the other hand, Y. Onuma et al. investigated the case of updating the
ECU with less processing time and to avoid any attacker exploiting exposed
vulnerabilities. This article emphasized on the weakness of in-vehicle networking
specially on ECUs update process [11].
For the last decade a lot of proposed solutions have been presented to improve
security of vehicle communications. In this regard, Zeng et al. have presented a
comprehensive survey discussing all in-vehicle networks based on three factors, system
cost, data transmission capacity, and fault-tolerance capability. Then they have assured
the importance of the gateway in connected vehicle, and finally presented some security
threats issues on the in-vehicle networks [12]. Their contribution was very clear about
the importance of having connected gateway and emphasizing on the importance of
security on in-vehicle communication.
Wang et al. have also proposed a distributed anomaly detection system using
hierarchical temporal memory (HTM) to enhance the security of a vehicular controller

area network bus [13]. The HTM model can predict the flow data in real time, which
depends on the state of the previous learning. This technique is also oriented to detect
and minimize the abnormal behavior inside the vehicle network. In addition, Woo et al.
showed that even wireless attack is physically possible using a real vehicle and
malicious smartphone application in a connected car environment. They proposed a
novel security protocol for CAN networks and used CANoe for the evaluation and
experiment. The result delivered promising security protocol better than existed one in
regards to authentication delay and communication load [14]. Many other security
proposals for securing communications have been demonstrated and achieved good
result which again spot on the importance of security in vehicle, such as [15], [16], [17],
[18]. Moreover, some significant topics describe secure communication with the cloud
and enhancing it with a secure storage concept, [28] and [29].
All of the above proposed methods and many more others have proven feasible
security improvement. However, the main issues of the authentication and processing
time are still existed. Therefore, Blockchain technology recently is the newest solution
to avoid the aforementioned issues. As a start, a good survey about involving
Blockchain in several applications to improve the security can be found in [19]. The
authors have provided an overview of the application domains of Blockchain
technologies in IoT, e.g. Internet of Vehicles, Internet of Energy, Internet of Cloud, Fog
computing. One of the professional solution that utilizes Blockchain is presented by S.
Alam in his thesis about securing in-vehicle communication [20]. The author proposes
the use of symmetric key cryptography and elliptic curve-based Public Key Encryption
(PKE) for ensuring confidentiality and the use of digital signature for ensuring integrity
and authenticity. He introduces Blockchain in vehicles to protect the stored data of
ECUs. The experiment study was conducted on Docker and ARM processor based
Raspberry Pei. In our proposed article, we have used the concept in [20] and improve
it not only to protect the data but also to control the communications between all ECUs.
According to other applications of Blockchain in vehicle, A. Dorri et al. [5] proposed
an optimized Blockchain instantiation for the Internet of Things (IoT) called
Lightweight Scalable Blockchain (LSB). It is a decentralized approach that secure and
preserve the privacy of all automotive ecosystem. They proposed the LSB approach
that solved the problem of high processing time of the consensus algorithm. Moreover,
they discussed some attack scenarios like DDoS and how the LSB method protect
against it. In our article, we will utilize also some concepts from the LSB in reducing
the processing time. However, we still believe that a centralized and private Blockchain
is suitable for in-vehicle networking. On the other side, M. Cebe et al. proposed a
permissioned Blockchain to manage all collected data by the vehicle [21]. They
integrated Vehicular Public Key Management (VPKI) to the proposed Blockchain to
provide membership establishment and privacy. Next, they designed a fragmented
ledger that will store detailed data related to vehicle such as maintenance
information/history, car diagnosis reports, etc. Z. Yang et al. have proposed a
decentralized trust management system in vehicular networks based on Blockchain
technique where vehicles can validate the received messages from neighboring vehicles
using Bayesian Inference Model [22]. In the before mentioned article, the proposed
method gather data from vehicles and rank it. Then they generate a block in the
Blockchain.

Finally, and unfortunately, we cannot cover all proposed work due to limitation and
space issue. However, further details and resources about using Blockchain in vehicle
security can be found in [23], [24], [25] and [26].
3 Proposed Blockchain Approach
In the domain-based architecture, ECUs are grouped by their functionalities and placed
in the same communication bus (called a domain). Every domain is controlled by a
controller, which is called a switch (domain controller). In this architecture, every ECU
collects data from its sensors, processes the data, takes a decision, and works on that
decision or sends the processed data to other ECUs. Nodes are connected through the
connected /central gateway (MasterNode). A node can send data to other nodes through
the MasterNode.
Since the number of switches or domain controllers in the current or future in-vehicle
communication architecture is limited and connected to one cGW (or may be many
cGWs), a centralized Blockchain with a single authority, i.e. permissioned, is feasible
and suites the internal structure of the vehicle. However, if we consider the vehicle
external communications with the infrastructure such V2X then a centralized approach
may not be suitable. From this point of view, the general overview o f our proposed
Blockchain approach is demonstrated in figure 2.
Fig. 2. Overview of proposed Blockchain Approach
In the previous figure, MasterNode is permitting the authority for each node to get
involved in the network or not. In addition, each node gets updated by the recent
Blockchain after a block is validated, approved and created then added to the

Blockchain. The MasterNode shares blocks with the nodes where the integrity is
preserved by the hashing mechanism applied. The internal structure of a single block
can be shown in figure 3.
Fig. 3. Internal Structure of a Single Block in the Chain
The procedure of how the approach works is described in the following points:
1. Every ECU sends encrypted and signed data to the corresponding Node to
preserve the confidentiality, integrity and authenticity
2. All ECUs data are stored in the Blockchain of each Node
3. Inter-communication between ECUs is only allowed when the Node grants
permission for its ECU
4. The MasterNode monitors and verifies all Nodes, say, all Blockchain data
with each Node is encrypted to avoid any impact between Nodes if one is
compromised.
5. MasterNode stores all public keys for all Nodes and ECUs to keep verify
their signatures and identity.
a. If ECU1 attached to Node1 needs to communicate with ECU3
attached to Node3, Node1 verifies ECU1 and ECU3 identity from
the MasterNode. Once verified, a permission is granted to ECU1.
b. ECU1 sends a transaction to Node1. Node1 in turn shares the
transaction with other Nodes to vote based on a consensus
algorithm, then based on voting, it will be validated, approved and
added to the transactions list.
c. After approval of all Nodes on group of transactions then a block is
added to the front of the Blockchain with the following information:
i. Hash value for the current block and previous block. In this
regard, each node has a copy of the blockchain, Merkle tree
is inside each block for integrity
ii. Block version and header added to the MasterNode for
monitoring and history issues
d. The communication is granted and executed in a way that ECU3
decrypt the transaction using its private key.

The following message sequence diagram in figure 4 shows the processes of
securing and validating communications between two ECUs.
Fig. 4. Message Sequence Diagram for secure communication between two nodes
The previous figure shows the main and simple process to secure the communication
between two nodes and how the MasterNode is monitoring the process and granting
accesses for each ECU.
- ECU1 and ECU3 need to communicate.
- ECU1 sends signed request to Node1 asking for permission
- Node1 asks the MasterNode if this communication is allowed
- MasterNode contains all public keys for all components. It verifies the signature
of ECU1 and ECU3 to preserve the authenticity and integrity.
- Once verified, MasterNode notifies Node1 and Node3 that both ECUs can
communicate. Moreover, it sends the public keys of the two ECUs for the nodes.
- Each node shares the public key with the ECU and grants it a permission to
communicate
- ECU1 can now encrypt the data using the public key of ECU3 and signs it using
its private key
- ECUs can now securely communicate
- All of these transactions will be validated and verified by the MasterNode and
once all nodes vote for validation, a new block is added to the Blockchain in the
MasterNode

- The hash value will be then calculated for the current block and the MasterNode
shares the updates with the Nodes.
- All communication between nodes and MasterNode is signed for identity
verification.
In the previous diagram, all communication is secured by asymmetric encryption and
the identity is verified by the signatures. And all transactions have been considered to
add a new block in the chain. Therefore, Confidentiality, Integrity and Authenticity are
all preserved and the MasterNode is monitoring and controlling all the process.
4 Secure Communication using proposed Blockchain Approach
For this case study, we adopted the secure communication process between two ECUs.
Both ECUs contains an MPC5646C microcontroller from NXP [27]. The process is
proposed by F. Juergen as displayed in figure 5.
Fig. 5. Secure Communication between two ECUs
The main idea of this method in figure 5 is to preserve integrity, authenticity and
confidentiality. The Cryptographic Service Engine (CSE) contains already from the
OEM all keys between all ECUs for communication. The symmetric encryption
shortages like using single-key for encryption and key distribution is known and have
been solved by asymmetric methods. Therefore, using public key method for
encryption and private key for signing in our approach is suitable and more feasible for
in-vehicle communication.
Applying our Blockchain approach in the previous process in figure 5 can be interpreted
as the following:
1- Central ECU sends a signed request together with a random number to the
intended Node
2- The intended Node verifies it and forwards it to the MasterNode
3- The MasterNode will validate the identity of Central ECU and encrypt the
random number with the public keys of central ECU and sensor ECU
4- MasterNode sends permission approval and the public key of central ECU to
the Node of sensor ECU. The same action for central ECU.
5- Each Node communicates with the related ECU with the following
information: permission granted, public key of other node, encrypted random
number.

6- Central ECU will decrypt the random number to verify MasterNode identity
7- Sensor ECU will decrypt the random number to verify MasterNode identity,
then it encrypts the random number again using central ECU public key.
8- Sensor ECU sends this to the central ECU, which in turn decrypt it to check
Sensor ECU identity
9- When everything is validated and verified, both ECU can now securely
communicate
10- All of the above transactions will be stored in one block and all Nodes vote
for approval.
11- If they are approved, the MasterNode will calculate a new hash value for all
transactions, then add a new block to the Blockchain and share it with all
Nodes
After applying our proposed approach, all components have been identified
(Authenticity), data is encrypted between ECUs (Confidentiality) and hash values have
been generated (Integrity).
5 Discussion and Conclusion
All communication between ECUs still suffer from security drawbacks like highly
processing time or preserving confidentiality, integrity and authenticity. We propose an
approach to assess the feasibility of a private Blockchain technology to overcome the
aforementioned drawbacks. Blockchain nodes in this approach are the cGW as
MasterNode and switches as Nodes. According to the nature of in-vehicle networking,
the best Blockchain structure is centralized where the permission is granted by the
MasterNode. We present a use case of how two ECUs can communicate together in a
secure communication channel and how the Blockchain interact in this regard. To
demonstrate the secure communication between ECUs, we present a message sequence
diagram to show all internal processes between the MasterNode and intended nodes.
Then, we apply the proposed approach on a real example from NXP microcontrollers.
All communications between ECUs are secure and valid, in which a block of all these
transactions has been created by the MasterNode and then added to the beginning of
the chain. Finally, MasterNode updates all Nodes with the latest Blockchain. So, the
processing time is minimized, and Confidentiality, Integrity and Authenticity are
preserved. We believe, the proposed Blockchain is feasible and can be applied on the
in-vehicle communication. As a future outlook, more improvements on the proposed
approach will be performed and a real experimental and comparison study will take
place to provide a practical evidence on the success of the approach.

References
1. Wolf, M., Weimerskirch, A., Paar, C.: Secure In-Vehicle Communication. In:
Lemke K., Paar C., Wolf M. (eds) Embedded Security in Cars. Springer,
Berlin, Heidelberg (2006)
2. Hank, P., Müller, S., Vermesan, O., Van Den Keybus, J.: Automotive
Ethernet: in-vehicle networking and smart mobility. In: DATE '13
Proceedings of the Conference on Design, Automation and Test in Europe, pp.
1735-1739, IEE, Grenoble, France (2013).
3. Wu, Z., Zhao, J., Zhu, Y., and Li, Q.: Research on Vehicle Cybersecurity
Based on Dedicated Security Hardware and ECDH Algorithm. In: Intelligent
and Connected Vehicles Symposium, SAE Technical Paper 2017-01-2005
(2017)
4. 101 Blockchains Homepage, https://101blockchains.com, last accessed
2018/12/12
5. Dorri, A., Steger, M., S. Kanhere, S., Jurdak, R.: BlockChain: A Distributed
Solution to Automotive Security and Privacy. IEEE Communications
Magazine 55(12),119-125 (2017)
6. Rajbahadur, G. K., Malton, A. J., Walenstein, A., Hassan, A. E.: A Survey of
Anomaly Detection for Connected Vehicle Cybersecurity and Safety. In: IEEE
Intelligent Vehicles Symposium (IV), pp. 421-426, Changshu, China (2018)
7. Thuen, C.: Commonalities in Vehicle Vulnerabilities. In: IOActive, Seattle,
USA, (2018)
8. Li, H., Lu, R., Mahmoud, M.: Security and Privacy of Connected Vehicular
Cloud Computing. In: IEEE Network 32(3), 4-6 (2018)
9. Singh, M., Kim, S.: Security Analysis of Intelligent Vehicles: Challenges and
Scope. In: International SoC Design Conference (ISOCC), pp. 13-14, Seoul,
South Korea (2017)
10. NXP Homepage, https://www.nxp.com/docs/en/white-
paper/FVNECUA4WP.pdf, last accessed 2018/12/12
11. Onuma, Y., Terashima, Y., Kiyohara, R.: ECU Software Updating in Future
Vehicle Networks. In: International Conference on Advanced Information
Networking and Applications Workshops (WAINA), pp. 35-40, Taipei,
Taiwan (2017)
12. Zeng, W., Khalid, M., Chowdhury, S.: In-Vehicle Networks Outlook:
Achievements and Challenegs. In: IEEE Communications Surveys &
Tutorials 18(3), 1552-1571 (2018)
13. Wang, C., Zhao, Z., Gong, L., Zhu, L., Liu, Z., Cheng, X.: A Distributed
Anomaly Detection System for In-Vehicle Network Using HTM. In: IEEE
Access 6, 9091-9098 (2017)
14. Woo, S., Jo, H. J., Lee, D. H.: A Practical Wireless Attack on the Connected
Car and Security Protocol for In-Vehicle CAN. In: IEEE Transactions On
Intelligent Transportation Systems 16(2), 993-1006 (2015)
15. Petit, J., Shladover, S. E.: Potential Cyberattacks on Automated Vehicles. In:
IEEE Transactions On Intelligent Transportation Systems 16(2), 546-556
(2015)

16. Dardanelli, A., Maggi, F., Tanelli, M., Zanero, S., Savaresi, S., Kochanek, R.,
Holz, T.: A Security Layer for Smartphone-to-Vehicle Communication Over
Bluetooth. In: IEEE Embedded Systems Letters 5(3), 34-37 (2013)
17. Fernández, P. J., Santa, J., Bernal, F., Skarmeta, A.: Securing Vehicular IPv6
Communications. In: IEEE Transactions On Dependable and Secure
Computing 13(1), 46-58 (2016)
18. Salem, M., Buehler, U.: Transforming voluminous data flow into continuous
connection vectors for IDS. In: International Journal of Internet Technology
and Secured Transactions 5 (4), 307 – 326 (2014)
19. Ferrag, M. A., Derdour, M., Mukherjee, M., Derhab, A., Maglaras, M.,
Janicke, H.: lockchain Technologies for the Internet of Things: Research
Issues and Challenges. In: CoRR - Computing Research Repository - arXiv,
1-14 (2018)
20. Alam, S.: Securing Vehicle Electronic Control Unit (ECU) Communications
and Stored Data. In: School of Computing, Queen's University, Kingston,
Ontario, Canada (2018)
21. Cebe, M., Erdin, E., Akkaya, K., Aksu, H., Uluagac, S.: Block4Forensic: An
Integrated Lightweight Blockchain Framework for Forensics Applications of
Connected Vehicles. In: IEEE Communications Magazine 56, 50-57 (2018)
22. Zhe Yang, K. Y., Lei, L., Zheng, K., Leung, V. C. M.: Blockchain-based
Decentralized Trust Management in Vehicular Networks. In: IEEE Internet of
Things (2018)
23. Jiang, T., Fang, H., Wang, H.: Blockchain-based Internet of Vehicles:
Distributed Network Architecture and Performance Analysis," IEEE Internet
of Things (2018)
24. CryptoTec Homepage, https://www.cryptotec.com/wp-
content/uploads/2018/01/Blockchain_for_Automotive_CryptoTec_EN.pdf,
Last accessed 2018/12/12
25. CUBE Homepage,
https://cryptorating.eu/whitepapers/CUBE/CUBEWhite_Paper-V1.3.pdf, last
accessed 2018/12/12
26. Sharma, P. K., Moon, S. Y., Park, J. H.: Block-VN: A Distributed Blockchain
Based Vehicular Network Architecture in Smart City. In: Journal of
Information Processing System 13(1), 184-195 (2017)
27. NXP Homepage, https://www.nxp.com/docs/en/supporting-
information/DWF13_AMF_AUT_T0112_Detroit.pdf, last accessed
2018/12/12
28. Wang, X. A., Yang, X., Li, C., Liu, Y., Ding, Y.: Improved functional proxy
re-encryption schemes for secure cloud data sharing. In: Comput. Sci. Inf.
Syst. 15(3): 585-614 (2018)
29. Wang, X. A., Liu, Y., Zhang, Z., Yang, X.: Improved group-oriented proofs
of cloud storage in IoT setting. In: Concurrency and Computation: Practice
and Experience 30(21) (2018)