PKI”. This solution manages trust dynamically in a distributed way and provides better
trust experience for users. Despite its contribution, this solution neglects the protection
of private data.
2.3 TEE Trust Execution Environment
TEE (Trust Execution Environment) [16] is a tamper-proof trusted execution processing environment. It runs on a separate kernel and it can be safely updated.
TEE resists all software and physical attacks. It represents a space for storage
execution and secure execution.
In this context, Hawk [10], which is the first TEE, is a smart contract system that
provides confidentiality by executing contracts off-chain and posting only zeroknowledge proofs on-chain. The zero-knowledge proofs in Hawk incurs very high
computational overhead. Additionally, it was designed for a single compute node called
the “manager” which must be trusted for privacy.
There are also some technical inefficiencies such as limited block size and transfer
cost. In addition, once the data is stored in the Blockchain, it cannot be modified. This
poses certain problems such as falsification during the execution of the contract. In
some cases, the contract needs data in real time. The most relevant solution is to store
the data off-chain and choose another execution platform more secure and more
relevant.
To ensure confidentiality and private data protection, Rifi et al. [11] offer a solution
that combines two technologies: Trust Execution Environment TEE and Blockchain,
from where data is stored and executed in TEE. It is a platform that ensures data
integrity; confidentiality and protection, but it is based on the centralization of data
storage. In [11], authors concluded that in order to apply Blockchain technology to EHealth, it should be public, and has three main keys: scalability, secure access to
medical data, and data privacy. In this article, the researchers prove that the Blockchain
does not have good performances in terms of storage. Therefore, they proposed to store
the data off-chain using the IPFS (Interplanetary File System). The new Blockchain
technology [15] applied in e-Health identifies new ways to share the distributed view of
health data and promotes the advancement of precision medicine, improving health and
preventing diseases.
2.4 IPFS
IPFS [12] (Interplanetary File system) is a decentralized file sharing platform. It
identifies files by their contents. To retrieve file locations and connectivity information
from the nodes, this system uses Distributed Hash Table (DHT).
As described in [13], the DHT is primarily a distributed key value store. It uses
node identifiers and keys. They must have the same length and a distance metric to
easily store and retrieve the information. A node tries to find the nodes in its vicinity,
when searching a value and a key. To do this; it uses buckets to keep track of the nodes
in the network. The spaces are organized so that each node in the network has precise
information about its immediate environment.
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trust experience for users. Despite its contribution, this solution neglects the protection
of private data.
2.3 TEE Trust Execution Environment
TEE (Trust Execution Environment) [16] is a tamper-proof trusted execution processing environment. It runs on a separate kernel and it can be safely updated.
TEE resists all software and physical attacks. It represents a space for storage
execution and secure execution.
In this context, Hawk [10], which is the first TEE, is a smart contract system that
provides confidentiality by executing contracts off-chain and posting only zeroknowledge proofs on-chain. The zero-knowledge proofs in Hawk incurs very high
computational overhead. Additionally, it was designed for a single compute node called
the “manager” which must be trusted for privacy.
There are also some technical inefficiencies such as limited block size and transfer
cost. In addition, once the data is stored in the Blockchain, it cannot be modified. This
poses certain problems such as falsification during the execution of the contract. In
some cases, the contract needs data in real time. The most relevant solution is to store
the data off-chain and choose another execution platform more secure and more
relevant.
To ensure confidentiality and private data protection, Rifi et al. [11] offer a solution
that combines two technologies: Trust Execution Environment TEE and Blockchain,
from where data is stored and executed in TEE. It is a platform that ensures data
integrity; confidentiality and protection, but it is based on the centralization of data
storage. In [11], authors concluded that in order to apply Blockchain technology to EHealth, it should be public, and has three main keys: scalability, secure access to
medical data, and data privacy. In this article, the researchers prove that the Blockchain
does not have good performances in terms of storage. Therefore, they proposed to store
the data off-chain using the IPFS (Interplanetary File System). The new Blockchain
technology [15] applied in e-Health identifies new ways to share the distributed view of
health data and promotes the advancement of precision medicine, improving health and
preventing diseases.
2.4 IPFS
IPFS [12] (Interplanetary File system) is a decentralized file sharing platform. It
identifies files by their contents. To retrieve file locations and connectivity information
from the nodes, this system uses Distributed Hash Table (DHT).
As described in [13], the DHT is primarily a distributed key value store. It uses
node identifiers and keys. They must have the same length and a distance metric to
easily store and retrieve the information. A node tries to find the nodes in its vicinity,
when searching a value and a key. To do this; it uses buckets to keep track of the nodes
in the network. The spaces are organized so that each node in the network has precise
information about its immediate environment.
280
F. Yahmed and M. Abid