CTB-PKI: Clustering and Trust Enabled Blockchain Based PKI System for Efficient Communication in P2P Network

The decentralization feature of public and private blockchain-based applications is achieved by selecting different nodes as validators or Certificate Authority (
$CA$
) for each transaction. Public blockchain uses Proof of Work (
$PoW$
) to search for the validator.
$PoW$
causes an enormous amount of energy. Therefore, Proof of Stake (
$PoS$
), and Proof of Authority (
$PoA$
) emerged as alternate solutions. Selection of a new
$CA$
using
$PoS$
or
$PoA$
algorithms for each transaction may improve transaction security. However, a network may have a large number of transactions and participants. Selecting a
$CA$
for each transaction using
$PoS$
or
$PoA$
may cause a significant amount of block propagation delay, which can reduce network efficiency drastically. This paper proposes a different approach to increase the efficiency of Blockchain-based Public Key Infrastructure (
$BC-PKI$
). The proposed approach creates clusters of participant nodes based on their validation time, response time, and trust. This method selects a cluster based on the budget of response time and validation time given by the node that intends to start a transaction. Thereafter, the node which has the highest trust in that cluster is chosen as a
$CA$
for the next transaction. Instead of searching on all participant nodes, our approach searches on the nodes of the chosen cluster which reduces the searching space of the
$CA$
selection process. This research work adopts a trust evaluation approach where the trust factor is quantified based on its experience and reputation. The node trust is reevaluated after every successful and unsuccessful transaction. A node that performs more successful transactions has more trust value. The node that has a higher trust value has a higher probability to be selected as a
$CA$
for a transaction. The trust reevaluation process is followed by the clustering process. The result shows the proposed approach can reduce ~38.5% response time and ~2.2% validation time as compared to infrastructure which does not implement clustering. Additionally, the proposed
$CTB-PKI$
can be used in Blockchain 2.0 and Blockchain 3.0-related applications.