1.2 Smart Contract
Szabo first introduced the term smart contract in 1994, where the smart contract is defined
as “a computerized transaction protocol that executes the terms of a contract” [4].
Smart contracts are compiled as byte codes and executed in EVM (Ethereum
Virtual Machine) located in miners’ computers, which is very similar to Java executed
in JVM. When the smart contract operates, it must be packaged by the miner and
written into the Blockchain. Each Blockchain in Ethereum has various functions and
purposes [5]. Compared with traditional contract, a smart contract is an executable code
stored and running in Blockchain. The smart contract may execute independently and
automatically without third parties, and these running results are irreversible on
Blockchain and are traceable by each participant. The main features of smart contract
are given as follows [6]: stability and deterministic features, the same input always
produces the same output. Because smart contracts are executable codes stored in
Blockchain, every network participant can inspect them. Meanwhile, all the interactions with a smart contract occur via signed messages on the Blockchain and thus every
participant can verify and trace the contract’s operations.
The structure of this paper is as follows. Section 2 presents a state of the art by
analyzing the current situation and motivation. Section 3 describes the steps of the new
solution and an e-health use-case. We present the security analysis of the proposed
solution in Sect. 4. Conclusion is drawn in Sect. 5.
2 State of the Art
We have conducted an intensive research to get the state of the art of Blockchain and
smart contracts applications. In the following, we present the existing solutions based
on the technologies chosen by researchers.
2.1 Centralized Database
The researchers in [8] propose a solution for digitizing certificates, in university use
case, in order to improve the conditions and make life much easier using the Blockchain and intelligent contracts. Therefore, it will be possible to have a certificate,
wherever the student is and whatever the time, with full security since the access to the
data will be done only when people are authorized.
It is true that this solution has contributions in terms of time and speed. However, in
our opinion, it does not ensure total security since it puts in danger the private data
when they are published in the Blockchain. In addition, the weak point of the solution
is the centralization since the data are recorded in the database of the university and if it
is broken down, nothing can be done.
2.2 PKI Public Key Infrastructure
Existing certificate mechanisms do not dynamically ensure the trustworthiness of a
certificate, to solve this weakness Ahmed et al. [9] offer the “smart contract assisted
Trust Execution Environment and Multi-party Computation
279
Szabo first introduced the term smart contract in 1994, where the smart contract is defined
as “a computerized transaction protocol that executes the terms of a contract” [4].
Smart contracts are compiled as byte codes and executed in EVM (Ethereum
Virtual Machine) located in miners’ computers, which is very similar to Java executed
in JVM. When the smart contract operates, it must be packaged by the miner and
written into the Blockchain. Each Blockchain in Ethereum has various functions and
purposes [5]. Compared with traditional contract, a smart contract is an executable code
stored and running in Blockchain. The smart contract may execute independently and
automatically without third parties, and these running results are irreversible on
Blockchain and are traceable by each participant. The main features of smart contract
are given as follows [6]: stability and deterministic features, the same input always
produces the same output. Because smart contracts are executable codes stored in
Blockchain, every network participant can inspect them. Meanwhile, all the interactions with a smart contract occur via signed messages on the Blockchain and thus every
participant can verify and trace the contract’s operations.
The structure of this paper is as follows. Section 2 presents a state of the art by
analyzing the current situation and motivation. Section 3 describes the steps of the new
solution and an e-health use-case. We present the security analysis of the proposed
solution in Sect. 4. Conclusion is drawn in Sect. 5.
2 State of the Art
We have conducted an intensive research to get the state of the art of Blockchain and
smart contracts applications. In the following, we present the existing solutions based
on the technologies chosen by researchers.
2.1 Centralized Database
The researchers in [8] propose a solution for digitizing certificates, in university use
case, in order to improve the conditions and make life much easier using the Blockchain and intelligent contracts. Therefore, it will be possible to have a certificate,
wherever the student is and whatever the time, with full security since the access to the
data will be done only when people are authorized.
It is true that this solution has contributions in terms of time and speed. However, in
our opinion, it does not ensure total security since it puts in danger the private data
when they are published in the Blockchain. In addition, the weak point of the solution
is the centralization since the data are recorded in the database of the university and if it
is broken down, nothing can be done.
2.2 PKI Public Key Infrastructure
Existing certificate mechanisms do not dynamically ensure the trustworthiness of a
certificate, to solve this weakness Ahmed et al. [9] offer the “smart contract assisted
Trust Execution Environment and Multi-party Computation
279