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Multi-tier Blockchain Framework for IoT-EHRs Systems
Available online at www.sciencedirect.com
ScienceDirect
Available online at www.sciencedirect.com Procedia Computer Science 00 (2018) 000–000
ScienceDirect
www.elsevier.com/locate/procedia
Procedia Computer Science 141 (2018) 159–166
The 9th International Conference on Emerging Ubiquitous Systems and Pervasive Networks (EUSPN 2018)
Multi-tier Blockchain Framework for IoT-EHRs Systems Shaimaa Badra,b,*,Ibrahim Gomaab,c , Emad Abd-Elrahmanb b
a Cairo University, 1 Gamaa Street, Giza, 12613, Egypt National Telecommunication Insttiute, 5 mahmoud Elmiligy st., 6th district, Nasr City, Cairo, 11768, Egypt c Helwan University, 1 Mostafa Fahmy, Helwan, Cairo, 11795, Egypyt
Abstract Recently, Blockchain is considered as one of the main powerful techniques in security and privacy domains. It is considered as the promised security concept for replacing the current third parities trusting solutions. This could be achieved by mixing some cryptography techniques, consensus algorithms alongside with some peer-to-peer communication protocols. In this paper, to meet the requirement of distributed structure in the eHealth Records (EHRs) system, we propose a novel protocol to achieve a perfect privacy preserving for the patient namely Pseudonym Based Encryption with Different Authorities (PBE-DA) by applying the concept of Blockchain on the healthcare communication entities in an e-health platform. Therefore, PBE-DA will be used to help the patient anonymously to access, check or update his sensitive data on EHRs system. Moreover, we analyzed not only the public blockchain tier between the different EHRs cloud provider but also another Blockchain tier between the patient sensors (IoT devices used to do some patient measurements) and the patient system as a gateway for the whole healthcare platform. © 2018 The Authors. Published by Elsevier Ltd. © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) This is anand open access article the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection peer-review underunder responsibility of the scientific committee of EUSPN 2018. Keywords: Blochchain; IoT; Healthcare;
1. Introduction Healthcare collaboration platform can be defined as the healthcare system that is capable of enabling the communication between healthcare entities like physicians, nurses, patients, medicines, labs, providers and healthcare authorities. Healthcare providers can implement different security measures in order to secure the communications between different entities. Either their front-end systems that responsible for communicating with
* Corresponding author. Tel.: +20-100-899-9395; fax: +20-238-921-40. E-mail address: [email protected] 1877-0509 © 2018 The Authors. Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the scientific committee of EUSPN 2018 1877-0509 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of EUSPN 2018. 10.1016/j.procs.2018.10.162
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physician or nurses or their back-end systems that hosts the eHealth Records (EHRs) can adopt blockchain security. This technology provides patients with comprehensive, immutable records and access to EHRs free from service providers and treatment websites. Regarding, anonymity, we found that in the Blockchain only pseudonymity is granted. Moreover, Blockchain can change the way that medical transactions occurred. It could guarantee the quality assurance for supporting electronic health records creating/retrieving/updating/deleting (CRUD) functions. In this paper, to guarantee the validity of Electronic Health Records (EHRs) encapsulated in blockchain and satisfy anonymous access to these records from cloud providers, we present the Pseudonym Based Encryption with Different Authorities (PBE-DA) approach. In PBE-DA, the logic for key generation and authentication is moved from the Internet of things (IoT) nodes to the corresponding gateway (GW), thus relieving the IoT device from the computational burden associated with the generation of cryptographic data. In addition, there are different authorities without a trusted single or central one (Private Key Generation: PKG) to generate and distribute public/private keys of the patient system, which avoids the escrow problem and conforms to the mode of distributed data storage in the Blockchain. Furthermore, PBE-DA will be used to create a patient virtual identity (PVID) that could help in preventing the reverse of access chain in the EHRs environment through hiding the main patient identity from cloud providers. This means that, instead of requesting a medical file for a known patient identity in unknown storage place (i.e. the cloud provider). We hope to execute a service with an unknown identity (PV ID) in cloud provider (an unknown) environment. The results and outcomes for PBE-DA showed that it is suitable paradigm for achieving high degree of efficiency and security in such sophisticated platforms for EHRs systems, which cope with Blockchain in IoT infrastructure design. The rest of this paper is organized as follows: Section 2 highlights the state of the art comparing to our architecture. Section 3 introduces our proposed framework including the main architecture for the Multi-tier blockchain details. In Section 4, we validate the framework through MIRACL security tools then; the processing times for PBE-DA messages is conducted in Section 5. Finally, this work is concluded with some perspectives in Section 6. 2. State of the art Securing IoT devices is one of the big challenges in cyber-security domains. The original Blockchain was part of the Bitcoin cryptocurrency design and provided only eventual consensus, although it tolerated Byzantine faults [1]. More recent Blockchain like Hyperledger Fabric already provide strong consensus [3]. There is a recent excitement with consensus and state machine replication in the context of cryptocurrencies and blockchain [1], [2], [3]. These systems use consensus to build a replicated ledger, which is essentially a log of transactions. The study analysis introduced in [11] for Blochchain with IoT answered many research questions raised in this research direction with different use cases in IoT scenarios. It mainly confirmed our thought about the pseudonymity of using Blockchain in IoT systems. The work in [8] provides a distributed Blockchain cloud architecture alongside with the emerging Software Defined Networking (SDN) technology. To cope with the Blockchain nature, the SDN controllers are connected in a distributed way using Blockchain technology. This work considered the conventional Blockchain for the proof of service such as such Ethereum [9] for the token exchanged between the Blockchain members. The EHR system proposed in [10] used separate Blockchain for each patient in which each one owns the chain by himself, after being treated in one hospital or any one of the authorities, all the information related to patient is encapsulated in one block. This system is considered as a Single-layer Blockchain based access control for each patient level. The work proposed in [12] studied the enhancement of anonymity of Blockchain for privacy protection in IoT systems. They considered Zero-Knowledge proof as a Blockchain anonymity enhancement technology, which can prevent security threats such as personal information infringement through block inquiry. The studied use case is the smart meter power pricing for secure charging in a Single-layer Blockchain based secure architecture. The concept for Blockchain based Multi-layer security in IoT network model was proposed in [13]. This work highlighted the de-centric model for IoT deployment. The Edge layer for this work is similar to our first tier layer in
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our model that considered the IoT devices attached to each patient in the access layer while the other higher layers are similar to the second tier in our model, which considered the authorities entities Blockchain in EHR systems. The authors in [14] proposed an IoT-chain architecture that is implemented the authorization Blockchain on top of a private Ethereum [9] blockchain network. Moreover, the work considered a Single-layer architecture for Blockchain based security between the entities. 3. Proposed Architecture The proposed framework architecture contains three tiers as shown in Figure 1: 1. Tier 1: The Constrained and Unconstrained nodes (Devices- Sensors) and Patient (Gateway - Aggregator) 2. Tier 2: N Authorities (Hospitals – Labs – Medical Insurance Organization – Medical Research Institute, …) 3. Tier 3: The EHRs cloud providers (Cloud Storage Servers for EHRs Records) We introduced Multi-tier Blockchain framework for IoT in EHRs Systems based PBE-DA using Elliptic Curve Cryptography (ECC). However, the ECC introduces equal or more security strength compared to other cryptography approaches. Therefore, ECC was chosen in the design of PBE-DA. MIRACL library [2] was used during the evaluation phase of the proposed solution to observe the processing times for all functions executed by different entities in the secure communication based Blockchain. MIRACL Library is a large number portable C library, which implements multi-precision integers, rational datatypes, and provides the routines to design large number cryptography into the real-world application. It is considered as the primary tool for cryptographic system implementers. MIRACL supports RSA, Diffie-Hellman Key exchange and the latest version offers full support for ECC over GF (p) and GF (2m). We propose three scenarios for this model: 1. Patient collects data from sensors to create EHR record from scratch. 2. Patient or authority need to access EHR record. 3. Patient adds a new block to his chain as a result of visiting an authority. Consequently, the same block will be added at all authorities and cloud provider. The EHRs system proposed model consists of four parties: 1. Constrained and Unconstrained nodes (Devices- Sensors): Internet of Things part, 2. Patient (Gateway/Aggregator) system, 3. N Authorities (Hospitals – Labs – Medical Insurance organization – Medical research Institute, …), 4. EHR Cloud providers (Cloud Storage Servers for EHRs Records).
Fig. 1. Multi-tier Blockchain Framework
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3.1. First tier: Blockchain-based platform for the edge Part This tier is represented by using private Blockchain methodology that covers the previous first scenario for new EHR record creation and used the block structure shown in Figure 2.(a) as follows: Sensors (devices) may be needed to complete initial registration to complete the block attributes (the hash of previous block, patient ID, Pseudonym, service and public key). As soon the registration is completed, the sensor can generate the patient private key. When the sensor needs to send data, it must authenticate itself at the patient (aggregator /gateway) system. Therefore, the sensor publishes the signature of pseudonym to the patient; the patient who has the public key which is equivalent to the private key used to create the signature will accept the data sent and authenticate the sender. 3.2. Second tier: Blockchain-based platform for the core Part This tier is represented by public Blockchain methodologies that can cover the second and third scenarios for either access or add new block using block architecture shown in Figure 2.(b) as follows: Assuming the patient has EHR record (contains data collected from sensors) and the same record created at visited authorities and cloud provider. Assuming that the patient visits one of authorities (hospitals, pharmaceutical departments, insurance departments, disease research departments and so on) which can be jointly managed. The visited hospital creates an EHR record for this patient on its system. In addition, it will send this record to a cloud provider. Therefore, the cloud provider creates the same record. All authorities can offer services for patients together and restrict the rights of each authority to prevent EHRs abuse. Authorized entity might look over the e-health records of this patient by means of his Blockchain, and has powerless to tamper the data in established block. Assuming that every patient owns one Blockchain of healthcare alone. After being treated in a hospital, all the information including hash of the EHR record, visit ID, patient ID, authority ID and date is encapsulated in one block. Patient treatments at different times will be generated in different blocks. Then, a series of blocks are generated according to the time sequence and a healthcare Blockchain of this patient is constructed. When the patient goes to be treated in other clinical departments or hospitals next time, the new entity needs to identify this patient and authenticate his available Blockchain, which could save the medical resources and avoid the repeated detection. To meet the requirement of distributed structure in EHRs system, we propose a novel protocol to achieve a perfect privacy preserving for the patient namely Pseudonym Based Encryption with different Authorities (PBEDA). In addition, PBE-DA will be used to help the patient anonymously to publish a block with sensitive data on EHRs system.
Fig. 2: (a). Edge Part Blockchain.
(b). Core Part Blockchain
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Patient chooses its virtual identity (as pseudonym) which used to help the patient anonymously to publish a block at EHR cloud provider; He chooses a random value K to compute its public key P pub = K.P and its private key as Ppriv = K.Q0 = K.S.P. The patient sends its patient ID, Pseudonym, service (which will be presented by an authority) and P pub to certain authority. The latter can calculate the patient’s private key because it is trusted by the patient, Ppriv = S. Ppub = K.S.P. The patient wants to be authenticated by the cloud provider, and then he sends its pseudonym along with a signature calculated by encrypting the pseudonym using his private key (we can use here the IBS: Identity Based Signature). The service provider asks for public key corresponding to the pseudonym from the visited authority, and then it verifies the signature by decrypting it using the patient’s public key. If it retrieves the pseudonym, then the authentication successes. The patient will add a new block to his Blockchain, authority Blockchain and cloud provider. Every patient owns his chain by himself after being treated in one authority. Therefore, all information related to the patient is encapsulated in one block such as the block shown in Figure 2.(b). When the patient wants to add block to the blockchain, the previous procedure will be adopted. This procedure could be triggered by other entities in the second tier chain. In this case, while a new block arrives, all participants in this chain must acknowledge the new arrival block for chain continuity. 3.3. Third tier: Blockchain-based cloud providers for e-health community In this tier, we propose using public Blockchain methodology to confirm the compliance issue between different EHR cloud providers (i.e. the community cloud deployment model between different e-health providers). More details for this tier will be considered in our future work. 4. Validations This section aims at evaluating a new Blockchain approach for IoT-EHRs environment. Therefore, PBE-DA is implemented, validated and verified using Multi-precision Integer and Rational Arithmetic C/C++ (MIRACL library) [5]. Hence, we introduced simple PBE before [4] as a cryptographic approach that could be used in accessing different types of services introduced by the integrity of cloud computing services access. MIRACL supports Elliptic Curve Diffie-Hellman (ECDH) key agreement protocol, Menezes-Vanstone Protocol and Elliptic Curve Digital Signature Algorithm (ECDSA), which we will utilize to implement and design the proposed protocol; PBE-DA. In order to evaluate the speed of the cryptographic operations, the PBE-DA is provided with “MIRACL library”, the communications between entities is modified and implemented. The elliptic curve (y2=x3-3x+bmod p) is used where (p) is a 256-bits prime number and (b) is determined through a function in MIRACL that can calculate the number of the points in a finite field which should be a prime number. 4.1. Implementation steps of PBE-DA Protocol The PBE-DA approach is based on PBE, which was proposed before for key management for anonymous communication in mobile ad-hoc networks [7]. The proposed approach contains four entities as shown in Figure 1: Sensors, Patient GW system, N Authorities and EHRs cloud provider. Implementation assumptions: 1. The constrained node is already authenticated with the patient Gateway (GW) system. 2. There exists a security policy allowing secure communications within the constrained network domain (and in particular between GW and the IoT sensors). 3. The gateway is a trusted entity which is the owned system by the patient.
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4.
An unconstrained node set up a secure connection with an IoT device while moving the master session key generation and authentication processes from the IoT node to the trusted gateway. Therefore, it can be involved in cryptographic key generation and authentication processes. According to Figure 3, the patient system (i.e. Gateway/Aggregator point) just computes the patient’s private key, which depends on its secret master key. The node (IoT device) wants to be authenticated by the patient; therefore, it uses an Identity-Based Signature (IBS) [6] to calculate the signature of pseudonym and sends to the patient. The patient verifies the signature by decrypting it using the public key (P pub). If it retrieves the pseudonym, then the authentication succeeds. Therefore, the patient will act as an authority who certifies that the node has the private key corresponding to his/her public key. Consequently, he accepts data from this node. Then the patient sends the data collected and request certain service from one of N authorities. Therefore, he sends patient identity, the requested service, the public key (Ppub) by choosing an elliptic curve with its generator point P and chooses his pseudonym. Authority calculates the patient’s private key (Ppriv) and doesn’t need to send the key pair (public/private) to the patient because the Ppub and Ppriv are already computed by the patient. The patient wants to be authenticated by the cloud provider; therefore, patient uses an Identity-Based Signature (IBS) to calculate the signature of pseudonym and sends it with the pseudonym to the cloud provider. The cloud provider sends pseudonym to the authority and asks for patient public key corresponding to the pseudonym. The cloud provider verifies the signature of pseudonym by decrypting it using the Ppub. If it retrieves the pseudonym, then the authentication succeeds. Since we use for this solution PBE-DA based ECC, we have to set up ECC. Therefore, we must first select a particular curve E over the finite field of order n, where n is a big prime number (GF (n)). We also pick an arbitrary generator point P on the curve as the base point of E and q (as an order of P). Moreover, we will use Elliptic Curve Digital Signature Algorithm (Ecdsa) for key generation, signature generation and signature verification. In order to satisfy this condition, we fixed a prime number (n) and the parameter (a) in elliptic curve. Then, we choose the parameter (b) in elliptic curve that satisfies this condition. We used a function in MIRACL that can calculate the number of the points in a finite field. Therefore, Elliptic curve point generation (Ecpg()) algorithm is developed to generate ECC point as detailed before in [4]. Then, we transfer to the next steps as follows: a) Key Extraction Given Patient ID and Requested eHealth Service (eSer), Pseudonym, Ppub: Patient Public Key, patient chooses random value k to calculate Ppub and Ppriv. Then, patient generates its parameters and keys by executing Elliptic Curve Digital Signature Algorithm Key Generation (EcdsaKgen()) to generate the patient’s Ppub and Ppriv as detailed in Table 1. b) Signature Generation In order to sign the patient pseudonym using a P priv derived from the patient to determine Pseudonym signature, the patient generates pseudonym, Ppub and Ppriv as following in Table 2. c) Signature Verification Once the EHR cloud provider receives the signature of pseudonym, it asks the authority for the public key for checking the signed pseudonym. Then, execute the Elliptic Curve Digital Signature Algorithm Signature verification to verify pseudonym’s signature (r, s) by performing the Algorithm EcdsaVer(pseudonym, Ppub) showed in Table 3.
Fig. 3. PBE-DA Framework.
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Table 1. EcdsaKgen() Algorithm 1: EcdsaKgen() 1: Choose elliptic curve E defined over GF(n) where n is a large prime number. 2: Select generator point P ϵ E (GF(n)), the order q (P is a point on elliptic curve) 3: Choose a random integer K ϵ [2, n-2] 4: Calculate S as a master secret key which involving in patient’s private keys generation 5: Compute the Patient’s public key Ppub= K.P, where K is a random value. 6: Compute the patient’s virtual identity PVID= Pseudonym 7: Compute the patient’s private key Ppriv= S*UP (S is the master secret key of patient) 8: Publish the patient’s public parameters (E,P,n,Ppub)
Table 2. EcdsaSign (Pseudonym, Ppub) Algorithm 2: EcdsaSign (Pseudonym, Ppub) 1: Generate n a large prime number 2: Calculate d= Ppriv mod (n-2) 3: Compute Q = d* Ppub 4: Select a statistically unique and unpredictable integer k in the interval [1, n-1]. 5: Compute the curve point k* Ppub = (x1, y1) and r = x1 mod n. If r = 0, then go to 4. (This is a security condition: if r = 0, then the signing equation: s = k-1*(H (Pseudonym) + d*r) mod n does not involve the private key). 6: Compute k-1 mod n. 7: Compute s = k-1*(H (Pseudonym) + d*r) mod n where H is the cryptographic hash function (SHA-2). If s = 0, then go to 4. (If s = 0, Then s-1 mod n does not exist; s-1 is required in iteration 2 of the signature verification.) 8: The signature for the virtual identity (Pseudonym) is the pair of integers (r, s) = Signature (Pseudonym) 9: Return Signature (Pseudonym) = (r, s)
Table 3. EcdsaVer (Pseudonym, Ppub) Algorithm 3: EcdsaVer (Pseudonym, Ppub) 1: Verify that r and s are integers in the interval [1, n-1]. If not, the signature is invalid. 2: Compute w = s-1 mod n 3: Calculate H(PVID), where H is the same hash function used in the signature generation. 4: Compute u1 = H(PVID)*w mod n and u2 = r*w mod n 5: Compute the curve point u1* Ppub + u2*Q = (x0, y0) and 6: EHR cloud provider accept the signature if and only if r= x0 mod n
5. Processing times for PBE-DA Resulting from MIRACL We used MIRACL Library during the evaluation of our solution’s performance to observe the processing time for all functions executed by different entities. The processing times for PBE-DA executing resulting from MIRACL are illustrated in Table 4. The results we got from calculating the total processing times for all messages are around 0.0715 Sec for all executed entities and functions for PBE-DA, using a computer machine with specs, Intel Core 2 Duo CPU E8400 @ 3.00GHz x 2, memory 4G in Linux Ubuntu 12.10. Table 4 showed the processing times for the PBE-DA as captured during the proposed scenario validation. The messages IDs sequence are shown in Figure 3.
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Table 4. Processing Times for PBE-DA Message ID
Source
Destination
Depends On
Processing Time (sec)
1 2
Nodes Patient
Patient Nodes
Beginning
N/A
3
Patient
One of N Authorities
ID:1
0.033
4
Patient
EHR cloud provider
ID:2
0.0015
5
EHR cloud provider
One of N Authorities
ID:3
0.028
6
One of N Authorities
EHR cloud provider
ID:4
0.009
Six messages total
0.0715
6. Conclusions and Future Work In this paper, a Multi-tier Blockchain based PBE-DA architecture is proposed and analyzed in terms of securing block based either creation or accessing using asymmetric security measure ECC. The first tier in our architecture considered the Fog or access layer for connecting the patient with his/her IoT devices through his/her gateway system. In the second tier, we analyzed the ledger communication or distribution between the EHRs members. Finally, the compliance issue is confirmed for the third tier between different EHR providers. The framework is validated using MIRACL security tools for different security functions. In the next work, we will detail each tier Blockchain over e-health platform with some IoT security countermeasures against some vulnerability. References 1. Nakamoto, Satoshi (2009) “Bitcoin: A Peer-to-Peer Electronic Cash System”, Cryptography Mailing list at https://metzdowd.com . 2. E. Peck, Morgen (2017) “Blockchains: How they work and why they'll change the world”, IEEE Spectrum. 54. 26-35. 10.1109/MSPEC.2017.8048836 3. Alysson Bessani, João Sousa, and Marko Vukolić. (2017) “A byzantine fault-tolerant ordering service for the hyperledger fabric blockchain platform” In Proceedings of the 1st Workshop on Scalable and Resilient Infrastructures for Distributed Ledgers (SERIAL '17). ACM, New York, NY, USA, Article 6, 2 pages. DOI: https://doi.org/10.1145/3152824.3152830 4. Ibrahim A. Gomaa, Emad Abd-Elrahman.(2015), “ A Novel Virtual Identity Implementation for Anonymous Communication in Cloud Environments. ” Proc. 6th Int. Conf. on Emerging Ubiquitous Systems and Pervasive Networks, EUSPN 2015. pp.32-39 5. “MIRACL | Authentication, SSO and Identity Access Management.” [Online]. Available: https://www.miracl.com/. [Accessed: 11-Jul-2018]. 6. Ibrahim A. Gomaa, Emad Abd-Elrahman, Mohamed Abid, “Virtual Identity Approaches Evaluation for Anonymous Communication in Cloud Environments.” (IJACSA) Int. J. of Advanced Computer Science and Applications, 2016.Vol. 7, pp. 367-376. 7. Huang, D., 2007. “Pseudonym-Based Cryptography for Anonymous Communications in Mobile Ad Hoc Networks”. Int. J. Secur. Netw. 2, 272–283. https://doi.org/10.1504/IJSN.2007.013180 8. Pradip Kumar Sharma, Mu-Yen Chen and Jong Hyuk Park,( 2018) “A Software Defined Fog Node Based Distributed Blockchain Cloud Architecture for IoT, ” in IEEE Access, vol. 6, pp. 115-124. 9.
GAVIN Wood. (2016). “Ethereum: a Secure Decentralised Generalised Transaction Ledger”. Tech. Report, Accessed: Jul. 11, 2018. [Online]. Available: http://gavwood.com/Paper.pdf.
10. Guo, R., Shi, H., Zhao, Q., Zheng, D., 2018. “Secure Attribute-Based Signature Scheme With Multiple Authorities for Blockchain in Electronic Health Records Systems”. IEEE Access vol. 6, pp 11676–11686. https://doi.org/10.1109/ACCESS.2018.2801266 11. M. Conoscenti, A. Vetrò and J. C. De Martin (2016) “Blockchain for the Internet of Things: A systematic literature review” 2016 IEEE/ACS 13th International Conference of Computer Systems and Applications (AICCSA), Agadir, pp. 1-6. 12. Lee, C.H., Kim, K.H., (2018). “Implementation of IoT system using block chain with authentication and data protection, ” in: 2018 International Conference on Information Networking (ICOIN). Presented at the 2018 International Conference on Information Networking (ICOIN), pp. 936–940. https://doi.org/10.1109/ICOIN.2018.8343261 13. Li, C., Zhang, L.J., (2017). “ A Blockchain Based New Secure Multi-Layer Network Model for Internet of Things, ” in: 2017 IEEE International Congress on Internet of Things (ICIOT). Presented at the 2017 IEEE International Congress on Internet of Things (ICIOT), pp. 33–41. https://doi.org/10.1109/IEEE.ICIOT.2017.34 14. Alphand, O., Amoretti, M., Claeys, T., Dall’Asta, S., Duda, A., Ferrari, G., Rousseau, F., Tourancheau, B., Veltri, L., Zanichelli, F., (2018). “ IoTChain: A blockchain security architecture for the Internet of Things, ” in: 2018 IEEE Wireless Communications and Networking Conference (WCNC). Presented at the 2018 IEEE Wireless Communications and Networking Conference (WCNC), pp. 1–6. https://doi.org/10.1109/WCNC.2018.8377385.
ScienceDirect
Available online at www.sciencedirect.com Procedia Computer Science 00 (2018) 000–000
ScienceDirect
www.elsevier.com/locate/procedia
Procedia Computer Science 141 (2018) 159–166
The 9th International Conference on Emerging Ubiquitous Systems and Pervasive Networks (EUSPN 2018)
Multi-tier Blockchain Framework for IoT-EHRs Systems Shaimaa Badra,b,*,Ibrahim Gomaab,c , Emad Abd-Elrahmanb b
a Cairo University, 1 Gamaa Street, Giza, 12613, Egypt National Telecommunication Insttiute, 5 mahmoud Elmiligy st., 6th district, Nasr City, Cairo, 11768, Egypt c Helwan University, 1 Mostafa Fahmy, Helwan, Cairo, 11795, Egypyt
Abstract Recently, Blockchain is considered as one of the main powerful techniques in security and privacy domains. It is considered as the promised security concept for replacing the current third parities trusting solutions. This could be achieved by mixing some cryptography techniques, consensus algorithms alongside with some peer-to-peer communication protocols. In this paper, to meet the requirement of distributed structure in the eHealth Records (EHRs) system, we propose a novel protocol to achieve a perfect privacy preserving for the patient namely Pseudonym Based Encryption with Different Authorities (PBE-DA) by applying the concept of Blockchain on the healthcare communication entities in an e-health platform. Therefore, PBE-DA will be used to help the patient anonymously to access, check or update his sensitive data on EHRs system. Moreover, we analyzed not only the public blockchain tier between the different EHRs cloud provider but also another Blockchain tier between the patient sensors (IoT devices used to do some patient measurements) and the patient system as a gateway for the whole healthcare platform. © 2018 The Authors. Published by Elsevier Ltd. © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) This is anand open access article the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection peer-review underunder responsibility of the scientific committee of EUSPN 2018. Keywords: Blochchain; IoT; Healthcare;
1. Introduction Healthcare collaboration platform can be defined as the healthcare system that is capable of enabling the communication between healthcare entities like physicians, nurses, patients, medicines, labs, providers and healthcare authorities. Healthcare providers can implement different security measures in order to secure the communications between different entities. Either their front-end systems that responsible for communicating with
* Corresponding author. Tel.: +20-100-899-9395; fax: +20-238-921-40. E-mail address: [email protected] 1877-0509 © 2018 The Authors. Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the scientific committee of EUSPN 2018 1877-0509 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of EUSPN 2018. 10.1016/j.procs.2018.10.162
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physician or nurses or their back-end systems that hosts the eHealth Records (EHRs) can adopt blockchain security. This technology provides patients with comprehensive, immutable records and access to EHRs free from service providers and treatment websites. Regarding, anonymity, we found that in the Blockchain only pseudonymity is granted. Moreover, Blockchain can change the way that medical transactions occurred. It could guarantee the quality assurance for supporting electronic health records creating/retrieving/updating/deleting (CRUD) functions. In this paper, to guarantee the validity of Electronic Health Records (EHRs) encapsulated in blockchain and satisfy anonymous access to these records from cloud providers, we present the Pseudonym Based Encryption with Different Authorities (PBE-DA) approach. In PBE-DA, the logic for key generation and authentication is moved from the Internet of things (IoT) nodes to the corresponding gateway (GW), thus relieving the IoT device from the computational burden associated with the generation of cryptographic data. In addition, there are different authorities without a trusted single or central one (Private Key Generation: PKG) to generate and distribute public/private keys of the patient system, which avoids the escrow problem and conforms to the mode of distributed data storage in the Blockchain. Furthermore, PBE-DA will be used to create a patient virtual identity (PVID) that could help in preventing the reverse of access chain in the EHRs environment through hiding the main patient identity from cloud providers. This means that, instead of requesting a medical file for a known patient identity in unknown storage place (i.e. the cloud provider). We hope to execute a service with an unknown identity (PV ID) in cloud provider (an unknown) environment. The results and outcomes for PBE-DA showed that it is suitable paradigm for achieving high degree of efficiency and security in such sophisticated platforms for EHRs systems, which cope with Blockchain in IoT infrastructure design. The rest of this paper is organized as follows: Section 2 highlights the state of the art comparing to our architecture. Section 3 introduces our proposed framework including the main architecture for the Multi-tier blockchain details. In Section 4, we validate the framework through MIRACL security tools then; the processing times for PBE-DA messages is conducted in Section 5. Finally, this work is concluded with some perspectives in Section 6. 2. State of the art Securing IoT devices is one of the big challenges in cyber-security domains. The original Blockchain was part of the Bitcoin cryptocurrency design and provided only eventual consensus, although it tolerated Byzantine faults [1]. More recent Blockchain like Hyperledger Fabric already provide strong consensus [3]. There is a recent excitement with consensus and state machine replication in the context of cryptocurrencies and blockchain [1], [2], [3]. These systems use consensus to build a replicated ledger, which is essentially a log of transactions. The study analysis introduced in [11] for Blochchain with IoT answered many research questions raised in this research direction with different use cases in IoT scenarios. It mainly confirmed our thought about the pseudonymity of using Blockchain in IoT systems. The work in [8] provides a distributed Blockchain cloud architecture alongside with the emerging Software Defined Networking (SDN) technology. To cope with the Blockchain nature, the SDN controllers are connected in a distributed way using Blockchain technology. This work considered the conventional Blockchain for the proof of service such as such Ethereum [9] for the token exchanged between the Blockchain members. The EHR system proposed in [10] used separate Blockchain for each patient in which each one owns the chain by himself, after being treated in one hospital or any one of the authorities, all the information related to patient is encapsulated in one block. This system is considered as a Single-layer Blockchain based access control for each patient level. The work proposed in [12] studied the enhancement of anonymity of Blockchain for privacy protection in IoT systems. They considered Zero-Knowledge proof as a Blockchain anonymity enhancement technology, which can prevent security threats such as personal information infringement through block inquiry. The studied use case is the smart meter power pricing for secure charging in a Single-layer Blockchain based secure architecture. The concept for Blockchain based Multi-layer security in IoT network model was proposed in [13]. This work highlighted the de-centric model for IoT deployment. The Edge layer for this work is similar to our first tier layer in
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our model that considered the IoT devices attached to each patient in the access layer while the other higher layers are similar to the second tier in our model, which considered the authorities entities Blockchain in EHR systems. The authors in [14] proposed an IoT-chain architecture that is implemented the authorization Blockchain on top of a private Ethereum [9] blockchain network. Moreover, the work considered a Single-layer architecture for Blockchain based security between the entities. 3. Proposed Architecture The proposed framework architecture contains three tiers as shown in Figure 1: 1. Tier 1: The Constrained and Unconstrained nodes (Devices- Sensors) and Patient (Gateway - Aggregator) 2. Tier 2: N Authorities (Hospitals – Labs – Medical Insurance Organization – Medical Research Institute, …) 3. Tier 3: The EHRs cloud providers (Cloud Storage Servers for EHRs Records) We introduced Multi-tier Blockchain framework for IoT in EHRs Systems based PBE-DA using Elliptic Curve Cryptography (ECC). However, the ECC introduces equal or more security strength compared to other cryptography approaches. Therefore, ECC was chosen in the design of PBE-DA. MIRACL library [2] was used during the evaluation phase of the proposed solution to observe the processing times for all functions executed by different entities in the secure communication based Blockchain. MIRACL Library is a large number portable C library, which implements multi-precision integers, rational datatypes, and provides the routines to design large number cryptography into the real-world application. It is considered as the primary tool for cryptographic system implementers. MIRACL supports RSA, Diffie-Hellman Key exchange and the latest version offers full support for ECC over GF (p) and GF (2m). We propose three scenarios for this model: 1. Patient collects data from sensors to create EHR record from scratch. 2. Patient or authority need to access EHR record. 3. Patient adds a new block to his chain as a result of visiting an authority. Consequently, the same block will be added at all authorities and cloud provider. The EHRs system proposed model consists of four parties: 1. Constrained and Unconstrained nodes (Devices- Sensors): Internet of Things part, 2. Patient (Gateway/Aggregator) system, 3. N Authorities (Hospitals – Labs – Medical Insurance organization – Medical research Institute, …), 4. EHR Cloud providers (Cloud Storage Servers for EHRs Records).
Fig. 1. Multi-tier Blockchain Framework
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3.1. First tier: Blockchain-based platform for the edge Part This tier is represented by using private Blockchain methodology that covers the previous first scenario for new EHR record creation and used the block structure shown in Figure 2.(a) as follows: Sensors (devices) may be needed to complete initial registration to complete the block attributes (the hash of previous block, patient ID, Pseudonym, service and public key). As soon the registration is completed, the sensor can generate the patient private key. When the sensor needs to send data, it must authenticate itself at the patient (aggregator /gateway) system. Therefore, the sensor publishes the signature of pseudonym to the patient; the patient who has the public key which is equivalent to the private key used to create the signature will accept the data sent and authenticate the sender. 3.2. Second tier: Blockchain-based platform for the core Part This tier is represented by public Blockchain methodologies that can cover the second and third scenarios for either access or add new block using block architecture shown in Figure 2.(b) as follows: Assuming the patient has EHR record (contains data collected from sensors) and the same record created at visited authorities and cloud provider. Assuming that the patient visits one of authorities (hospitals, pharmaceutical departments, insurance departments, disease research departments and so on) which can be jointly managed. The visited hospital creates an EHR record for this patient on its system. In addition, it will send this record to a cloud provider. Therefore, the cloud provider creates the same record. All authorities can offer services for patients together and restrict the rights of each authority to prevent EHRs abuse. Authorized entity might look over the e-health records of this patient by means of his Blockchain, and has powerless to tamper the data in established block. Assuming that every patient owns one Blockchain of healthcare alone. After being treated in a hospital, all the information including hash of the EHR record, visit ID, patient ID, authority ID and date is encapsulated in one block. Patient treatments at different times will be generated in different blocks. Then, a series of blocks are generated according to the time sequence and a healthcare Blockchain of this patient is constructed. When the patient goes to be treated in other clinical departments or hospitals next time, the new entity needs to identify this patient and authenticate his available Blockchain, which could save the medical resources and avoid the repeated detection. To meet the requirement of distributed structure in EHRs system, we propose a novel protocol to achieve a perfect privacy preserving for the patient namely Pseudonym Based Encryption with different Authorities (PBEDA). In addition, PBE-DA will be used to help the patient anonymously to publish a block with sensitive data on EHRs system.
Fig. 2: (a). Edge Part Blockchain.
(b). Core Part Blockchain
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Patient chooses its virtual identity (as pseudonym) which used to help the patient anonymously to publish a block at EHR cloud provider; He chooses a random value K to compute its public key P pub = K.P and its private key as Ppriv = K.Q0 = K.S.P. The patient sends its patient ID, Pseudonym, service (which will be presented by an authority) and P pub to certain authority. The latter can calculate the patient’s private key because it is trusted by the patient, Ppriv = S. Ppub = K.S.P. The patient wants to be authenticated by the cloud provider, and then he sends its pseudonym along with a signature calculated by encrypting the pseudonym using his private key (we can use here the IBS: Identity Based Signature). The service provider asks for public key corresponding to the pseudonym from the visited authority, and then it verifies the signature by decrypting it using the patient’s public key. If it retrieves the pseudonym, then the authentication successes. The patient will add a new block to his Blockchain, authority Blockchain and cloud provider. Every patient owns his chain by himself after being treated in one authority. Therefore, all information related to the patient is encapsulated in one block such as the block shown in Figure 2.(b). When the patient wants to add block to the blockchain, the previous procedure will be adopted. This procedure could be triggered by other entities in the second tier chain. In this case, while a new block arrives, all participants in this chain must acknowledge the new arrival block for chain continuity. 3.3. Third tier: Blockchain-based cloud providers for e-health community In this tier, we propose using public Blockchain methodology to confirm the compliance issue between different EHR cloud providers (i.e. the community cloud deployment model between different e-health providers). More details for this tier will be considered in our future work. 4. Validations This section aims at evaluating a new Blockchain approach for IoT-EHRs environment. Therefore, PBE-DA is implemented, validated and verified using Multi-precision Integer and Rational Arithmetic C/C++ (MIRACL library) [5]. Hence, we introduced simple PBE before [4] as a cryptographic approach that could be used in accessing different types of services introduced by the integrity of cloud computing services access. MIRACL supports Elliptic Curve Diffie-Hellman (ECDH) key agreement protocol, Menezes-Vanstone Protocol and Elliptic Curve Digital Signature Algorithm (ECDSA), which we will utilize to implement and design the proposed protocol; PBE-DA. In order to evaluate the speed of the cryptographic operations, the PBE-DA is provided with “MIRACL library”, the communications between entities is modified and implemented. The elliptic curve (y2=x3-3x+bmod p) is used where (p) is a 256-bits prime number and (b) is determined through a function in MIRACL that can calculate the number of the points in a finite field which should be a prime number. 4.1. Implementation steps of PBE-DA Protocol The PBE-DA approach is based on PBE, which was proposed before for key management for anonymous communication in mobile ad-hoc networks [7]. The proposed approach contains four entities as shown in Figure 1: Sensors, Patient GW system, N Authorities and EHRs cloud provider. Implementation assumptions: 1. The constrained node is already authenticated with the patient Gateway (GW) system. 2. There exists a security policy allowing secure communications within the constrained network domain (and in particular between GW and the IoT sensors). 3. The gateway is a trusted entity which is the owned system by the patient.
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4.
An unconstrained node set up a secure connection with an IoT device while moving the master session key generation and authentication processes from the IoT node to the trusted gateway. Therefore, it can be involved in cryptographic key generation and authentication processes. According to Figure 3, the patient system (i.e. Gateway/Aggregator point) just computes the patient’s private key, which depends on its secret master key. The node (IoT device) wants to be authenticated by the patient; therefore, it uses an Identity-Based Signature (IBS) [6] to calculate the signature of pseudonym and sends to the patient. The patient verifies the signature by decrypting it using the public key (P pub). If it retrieves the pseudonym, then the authentication succeeds. Therefore, the patient will act as an authority who certifies that the node has the private key corresponding to his/her public key. Consequently, he accepts data from this node. Then the patient sends the data collected and request certain service from one of N authorities. Therefore, he sends patient identity, the requested service, the public key (Ppub) by choosing an elliptic curve with its generator point P and chooses his pseudonym. Authority calculates the patient’s private key (Ppriv) and doesn’t need to send the key pair (public/private) to the patient because the Ppub and Ppriv are already computed by the patient. The patient wants to be authenticated by the cloud provider; therefore, patient uses an Identity-Based Signature (IBS) to calculate the signature of pseudonym and sends it with the pseudonym to the cloud provider. The cloud provider sends pseudonym to the authority and asks for patient public key corresponding to the pseudonym. The cloud provider verifies the signature of pseudonym by decrypting it using the Ppub. If it retrieves the pseudonym, then the authentication succeeds. Since we use for this solution PBE-DA based ECC, we have to set up ECC. Therefore, we must first select a particular curve E over the finite field of order n, where n is a big prime number (GF (n)). We also pick an arbitrary generator point P on the curve as the base point of E and q (as an order of P). Moreover, we will use Elliptic Curve Digital Signature Algorithm (Ecdsa) for key generation, signature generation and signature verification. In order to satisfy this condition, we fixed a prime number (n) and the parameter (a) in elliptic curve. Then, we choose the parameter (b) in elliptic curve that satisfies this condition. We used a function in MIRACL that can calculate the number of the points in a finite field. Therefore, Elliptic curve point generation (Ecpg()) algorithm is developed to generate ECC point as detailed before in [4]. Then, we transfer to the next steps as follows: a) Key Extraction Given Patient ID and Requested eHealth Service (eSer), Pseudonym, Ppub: Patient Public Key, patient chooses random value k to calculate Ppub and Ppriv. Then, patient generates its parameters and keys by executing Elliptic Curve Digital Signature Algorithm Key Generation (EcdsaKgen()) to generate the patient’s Ppub and Ppriv as detailed in Table 1. b) Signature Generation In order to sign the patient pseudonym using a P priv derived from the patient to determine Pseudonym signature, the patient generates pseudonym, Ppub and Ppriv as following in Table 2. c) Signature Verification Once the EHR cloud provider receives the signature of pseudonym, it asks the authority for the public key for checking the signed pseudonym. Then, execute the Elliptic Curve Digital Signature Algorithm Signature verification to verify pseudonym’s signature (r, s) by performing the Algorithm EcdsaVer(pseudonym, Ppub) showed in Table 3.
Fig. 3. PBE-DA Framework.
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Table 1. EcdsaKgen() Algorithm 1: EcdsaKgen() 1: Choose elliptic curve E defined over GF(n) where n is a large prime number. 2: Select generator point P ϵ E (GF(n)), the order q (P is a point on elliptic curve) 3: Choose a random integer K ϵ [2, n-2] 4: Calculate S as a master secret key which involving in patient’s private keys generation 5: Compute the Patient’s public key Ppub= K.P, where K is a random value. 6: Compute the patient’s virtual identity PVID= Pseudonym 7: Compute the patient’s private key Ppriv= S*UP (S is the master secret key of patient) 8: Publish the patient’s public parameters (E,P,n,Ppub)
Table 2. EcdsaSign (Pseudonym, Ppub) Algorithm 2: EcdsaSign (Pseudonym, Ppub) 1: Generate n a large prime number 2: Calculate d= Ppriv mod (n-2) 3: Compute Q = d* Ppub 4: Select a statistically unique and unpredictable integer k in the interval [1, n-1]. 5: Compute the curve point k* Ppub = (x1, y1) and r = x1 mod n. If r = 0, then go to 4. (This is a security condition: if r = 0, then the signing equation: s = k-1*(H (Pseudonym) + d*r) mod n does not involve the private key). 6: Compute k-1 mod n. 7: Compute s = k-1*(H (Pseudonym) + d*r) mod n where H is the cryptographic hash function (SHA-2). If s = 0, then go to 4. (If s = 0, Then s-1 mod n does not exist; s-1 is required in iteration 2 of the signature verification.) 8: The signature for the virtual identity (Pseudonym) is the pair of integers (r, s) = Signature (Pseudonym) 9: Return Signature (Pseudonym) = (r, s)
Table 3. EcdsaVer (Pseudonym, Ppub) Algorithm 3: EcdsaVer (Pseudonym, Ppub) 1: Verify that r and s are integers in the interval [1, n-1]. If not, the signature is invalid. 2: Compute w = s-1 mod n 3: Calculate H(PVID), where H is the same hash function used in the signature generation. 4: Compute u1 = H(PVID)*w mod n and u2 = r*w mod n 5: Compute the curve point u1* Ppub + u2*Q = (x0, y0) and 6: EHR cloud provider accept the signature if and only if r= x0 mod n
5. Processing times for PBE-DA Resulting from MIRACL We used MIRACL Library during the evaluation of our solution’s performance to observe the processing time for all functions executed by different entities. The processing times for PBE-DA executing resulting from MIRACL are illustrated in Table 4. The results we got from calculating the total processing times for all messages are around 0.0715 Sec for all executed entities and functions for PBE-DA, using a computer machine with specs, Intel Core 2 Duo CPU E8400 @ 3.00GHz x 2, memory 4G in Linux Ubuntu 12.10. Table 4 showed the processing times for the PBE-DA as captured during the proposed scenario validation. The messages IDs sequence are shown in Figure 3.
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Table 4. Processing Times for PBE-DA Message ID
Source
Destination
Depends On
Processing Time (sec)
1 2
Nodes Patient
Patient Nodes
Beginning
N/A
3
Patient
One of N Authorities
ID:1
0.033
4
Patient
EHR cloud provider
ID:2
0.0015
5
EHR cloud provider
One of N Authorities
ID:3
0.028
6
One of N Authorities
EHR cloud provider
ID:4
0.009
Six messages total
0.0715
6. Conclusions and Future Work In this paper, a Multi-tier Blockchain based PBE-DA architecture is proposed and analyzed in terms of securing block based either creation or accessing using asymmetric security measure ECC. The first tier in our architecture considered the Fog or access layer for connecting the patient with his/her IoT devices through his/her gateway system. In the second tier, we analyzed the ledger communication or distribution between the EHRs members. Finally, the compliance issue is confirmed for the third tier between different EHR providers. The framework is validated using MIRACL security tools for different security functions. In the next work, we will detail each tier Blockchain over e-health platform with some IoT security countermeasures against some vulnerability. References 1. Nakamoto, Satoshi (2009) “Bitcoin: A Peer-to-Peer Electronic Cash System”, Cryptography Mailing list at https://metzdowd.com . 2. E. Peck, Morgen (2017) “Blockchains: How they work and why they'll change the world”, IEEE Spectrum. 54. 26-35. 10.1109/MSPEC.2017.8048836 3. Alysson Bessani, João Sousa, and Marko Vukolić. (2017) “A byzantine fault-tolerant ordering service for the hyperledger fabric blockchain platform” In Proceedings of the 1st Workshop on Scalable and Resilient Infrastructures for Distributed Ledgers (SERIAL '17). ACM, New York, NY, USA, Article 6, 2 pages. DOI: https://doi.org/10.1145/3152824.3152830 4. Ibrahim A. Gomaa, Emad Abd-Elrahman.(2015), “ A Novel Virtual Identity Implementation for Anonymous Communication in Cloud Environments. ” Proc. 6th Int. Conf. on Emerging Ubiquitous Systems and Pervasive Networks, EUSPN 2015. pp.32-39 5. “MIRACL | Authentication, SSO and Identity Access Management.” [Online]. Available: https://www.miracl.com/. [Accessed: 11-Jul-2018]. 6. Ibrahim A. Gomaa, Emad Abd-Elrahman, Mohamed Abid, “Virtual Identity Approaches Evaluation for Anonymous Communication in Cloud Environments.” (IJACSA) Int. J. of Advanced Computer Science and Applications, 2016.Vol. 7, pp. 367-376. 7. Huang, D., 2007. “Pseudonym-Based Cryptography for Anonymous Communications in Mobile Ad Hoc Networks”. Int. J. Secur. Netw. 2, 272–283. https://doi.org/10.1504/IJSN.2007.013180 8. Pradip Kumar Sharma, Mu-Yen Chen and Jong Hyuk Park,( 2018) “A Software Defined Fog Node Based Distributed Blockchain Cloud Architecture for IoT, ” in IEEE Access, vol. 6, pp. 115-124. 9.
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