  In the era of social media and messaging applications, people are becoming
increasingly aware of data privacy issues associated with such apps. Major
messaging applications are moving towards end-to-end encryption (E2EE) to give
their users the privacy they are demanding. However the current security
mechanisms employed by different service providers are not unfeigned E2EE
implementations, and are blended with many vulnerabilities. In the present
scenario, the major part of the E2EE mechanism is controlled by the service
provider's servers, and the decryption keys are stored by them in case of
backup restoration. These shortcomings diminish the user's confidence in the
privacy of their data while using these apps. A public Key infrastructure (PKI)
mechanism can be used to circumvent some of these issues, but it comes with
high monetary costs, which makes it impossible to roll out for millions of
users. The paper proposes a blockchain-based E2EE framework that can mitigate
the contemporary vulnerabilities in messaging applications. The user's device
generates the public/private key pair during application installation, and asks
its mobile network operator (MNO) to issue a digital certificate and store it
on the blockchain. A user can fetch a certificate for another user from the
chat server and communicate securely with them using a ratchet forward
encryption mechanism.
