Development of NavIC synchronized fully automated inter-building QKD framework and demonstration of quantum secured video calling

Quantum key distribution (QKD) is a revolutionary communication technology that promises ultimate security assurance by exploiting the fundamental principles of quantum mechanics. In this work, we report design and development of a fully automated inter-building QKD framework for generation and distribution of cryptographic keys, securely and seamlessly, by executing weak coherent pulse based BB84 protocol. This framework is experimentally validated by establishing a quantum communication link between two buildings separated by ~300m of free-space atmospheric channel. A novel synchronization technique enabled with indigenous NavIC (IRNSS) constellation is developed and implemented. This QKD system demonstrates generation of secure key rate as high as 300 Kbps with QBER< 3% for mean photon no. per pulse (${\mu}$) of 0.15. The intercept-resend eavesdropping attack has been emulated within the system and evaluated during experiment. A novel quantum secured end-to-end encrypted video calling app (QuViC) is also developed and integrated with QKD framework to demonstrate unconditionally secure two-way communication over Ethernet, functioning alongside with quantum communication.