Blockchain for IoMT: A Technical Review
263
The patient data are stored as strings in blocks in the blockchain and the IoMT
data are stored in blocks in off-chain database like IPFS. Smart contracts are
used to ensure the privacy and security of blockchain.
MedChain [18] is a consortium blockchain-based framework proposed to meet
challenges related to efficiently sharing data streams continuously generated
from medical sensors. This includes handling time-series data streams, managing mutable and immutable medical data, and allowing an efficient storage and
sharing of big and sensitive data. The MedChain network includes two separate
decentralized sub-networks: (1) Blockchain network to store immutable data
including users identity, data digest, session and operation, and (2) P2P network to store mutable data that facilitates data query including the description
of data and session. MedChain uses the BFT-SMaRt as a consensus protocol
BIoMT [17] is an optimized, lightweight blockchain-based framework proposed to meet security and privacy challenges in developing solutions for IoMT
systems. The proposed architecture is made up of four stratum: (1) Device
layer consists of IoMT devices and implements the Elliptic Curve Cryptography (ECC) [9] key establishment protocol and the identity-based credential
(IBC) mechanism to provide decentralized privacy, (2) Facility layer for managing IoMT devices and providing unique identity based on their attributes,
(3) Cloud layer that runs anonymization algorithms to allow an identity-free
data analysis and storage, and (4) Cluster layer groups several entities including
medical facilities, service providers, and cloud servers into clusters. Each cluster has a cluster head that manages communication with other cluster heads
to decrease the network overhead and delay. This work does not provide any
technical details. It is not implemented and not evaluated. In [4] and [19], a
blockchain-based architecture is proposed to allow secure transmission and storage of large amount of sensitive data generated by IoMT.
4 Discussion and Open Issues
Table 1 presents a classification of the existing contributions having integrated
blockchain to IoMT (NM means Not Mentioned). Most of the proposed solutions
are private blockchain-based and used Ethereum infrastructure thanks to its flexibility that is offered by the implementation of smart contracts for management
purposes. Many issues have been treated when integrating blockchain with IoMT.
For storing the big IoMT data, most of works [3] proposed an off-chain storage: Some researches [7,12] proposed to use IPFS because of its distributed data
structure. Other works [3,5,9,17,20] used the cloud computing to store encrypted
data while keeping hash references of that data in the blockchain. Such solutions
do not guarantee immutability which is the essential feature of blockchain. In
fact, if data have been modified/altered, this will be detected thanks to their
hash stored in the blockchain but not recovered as it is only stored in the cloud
(centralized storage). Other studies proposed an on-chain storage without precising technical details about dealing with the huge amount of data streams
generated by IoMT devices. In the other hand, healthcare applications require
263
The patient data are stored as strings in blocks in the blockchain and the IoMT
data are stored in blocks in off-chain database like IPFS. Smart contracts are
used to ensure the privacy and security of blockchain.
MedChain [18] is a consortium blockchain-based framework proposed to meet
challenges related to efficiently sharing data streams continuously generated
from medical sensors. This includes handling time-series data streams, managing mutable and immutable medical data, and allowing an efficient storage and
sharing of big and sensitive data. The MedChain network includes two separate
decentralized sub-networks: (1) Blockchain network to store immutable data
including users identity, data digest, session and operation, and (2) P2P network to store mutable data that facilitates data query including the description
of data and session. MedChain uses the BFT-SMaRt as a consensus protocol
BIoMT [17] is an optimized, lightweight blockchain-based framework proposed to meet security and privacy challenges in developing solutions for IoMT
systems. The proposed architecture is made up of four stratum: (1) Device
layer consists of IoMT devices and implements the Elliptic Curve Cryptography (ECC) [9] key establishment protocol and the identity-based credential
(IBC) mechanism to provide decentralized privacy, (2) Facility layer for managing IoMT devices and providing unique identity based on their attributes,
(3) Cloud layer that runs anonymization algorithms to allow an identity-free
data analysis and storage, and (4) Cluster layer groups several entities including
medical facilities, service providers, and cloud servers into clusters. Each cluster has a cluster head that manages communication with other cluster heads
to decrease the network overhead and delay. This work does not provide any
technical details. It is not implemented and not evaluated. In [4] and [19], a
blockchain-based architecture is proposed to allow secure transmission and storage of large amount of sensitive data generated by IoMT.
4 Discussion and Open Issues
Table 1 presents a classification of the existing contributions having integrated
blockchain to IoMT (NM means Not Mentioned). Most of the proposed solutions
are private blockchain-based and used Ethereum infrastructure thanks to its flexibility that is offered by the implementation of smart contracts for management
purposes. Many issues have been treated when integrating blockchain with IoMT.
For storing the big IoMT data, most of works [3] proposed an off-chain storage: Some researches [7,12] proposed to use IPFS because of its distributed data
structure. Other works [3,5,9,17,20] used the cloud computing to store encrypted
data while keeping hash references of that data in the blockchain. Such solutions
do not guarantee immutability which is the essential feature of blockchain. In
fact, if data have been modified/altered, this will be detected thanks to their
hash stored in the blockchain but not recovered as it is only stored in the cloud
(centralized storage). Other studies proposed an on-chain storage without precising technical details about dealing with the huge amount of data streams
generated by IoMT devices. In the other hand, healthcare applications require