IEEE Consumer Electronics Magazine - March/April 2023 - 90

Special Section on Security, Trust and Services for AI-Empowered Sensing in the Next Generation IoT
TABLE 3. Gas cost with different number of certificates.
No. of
certificates
1
10
20
30
40
50
100
Gas limit
(units)
22,645
218,730
419,660
619,290
825,720
Gas cost
147,633
1,389,224
2,752,440
4,128,660
5,504,880
1,032,150 6,881,100
2,064,300 13,762,200
Gas price
(CGWEI)
100
1000
2000
3000
4000
5000
10,000
depending on the supply and demand of the
computational power of the blockchain network
to process smart contracts. It is observed that
the proposed architecture's operational cost
increases by increasing the number of certificates.
The gas cost of these operations has been
retrieved by deploying the smart contracts of
related transactions over the blockchain network
through the MA. This experiment uses the BlockSim
toolkit to execute the smart contract functions
and analyzes the cost required for each operation.
Figure 2 presents the total gas cost analysis of
the proposed scheme by varying the certificate
generation and verification transactions in the
blockchain network. Gas consumption is measured
in the unit of Eths. The total gas
consumption of the proposed architecture is calculated
by varying the number of certificates ranging
from 20 to 160. Here, the certificate generation
and verification transactions are executed randomly
using the BlockSim toolkit. It is observed
that the proposed architecture requires more gas
consumption for the certificate generation transactions
than the verification transactions. This is
because it requires more processing power for
calculating the hash of the generated certificate,
mapping the user details with the certificate, and
generating a new block. Thus, the gas consumption
is higher due to a large number of computations
in the certificate generation transaction
compared to the verification transaction.
The processing time refers to the time
required to initiate the transaction until the user
gets the transaction execution ID. The processing
time of the proposed scheme's transactions
is analyzed for certificate generation and
90
FIGURE 2. Total gas cost of the proposedarchitecture
formedical certificates.
verification. The processing time is calculated
between the interval of transactions requested
and executed by the blockchain network for
each set of transactions. It is analyzed that the
certificate generation transactions require more
processing time than the verification transactions
due to the calculation involved to generate
hash values for the certificates. Furthermore,
certificate generation transactions involve blockchain
nodes or miners to validate communications
over the blockchain network by solving a
back-end mathematical puzzle and placing these
transactions into a new block. Then, the block is
added to the blockchain network. Thus, the
processing time also depends on the system
configuration, the number of transactions, and
miners' availability.
Table 4 presents the smart contract cost analysis
of the proposed architecture based on the
transaction generation cost and execution cost in
terms of gas. The transaction cost denotes the
cost of requesting the transaction in the blockchain
network, and the execution cost refers to
the total cost required to execute the corresponding
smart contract transaction. The BlockSim
toolkit is utilized to randomly calculate the transaction
cost and execution cost for different smart
contract operations.
Latency represents the delay between the
transaction requests and transaction appearances
on the blockchain network. In the proposed
architecture, 200 transactions are considered
to calculate the latency. All the transactions are
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