  In last two decades, messaging systems have gained widespread popularity both
in the enterprise and consumer sectors. Many of these systems used secure
protocols like end-to-end encryption to ensure strong security in one-to-one
communication. However, the majority of them rely on centralized servers, which
allows them to use their users' personal data. Also, it allows the government
to track and regulate their citizens' activities, which poses significant
threats to "digital freedom". Also, these systems have failed to achieve
security attributes like confidentiality, integrity, and privacy for group
communications. In this paper, we present a novel blockchain-based secure
messaging system named Quarks that overcomes the security pitfalls of the
existing systems and eliminates centralized control. We have analyzed our
architecture with security models to demonstrate the system's reliability and
usability. We have developed a Proof of Concept (PoC) of the Quarks system
leveraging Distributed Ledger Technology (DLT) and conducted load testing on
that. We noticed that our PoC system achieves all the desired attributes that
are prevalent in a traditional centralized messaging scheme despite the limited
capacity of the development and testing environment. Therefore, this assures us
of the applicability of such systems in the near future if scaled up properly.
