Impact of BB84 QKD transmitter’s parameter mismatch on secure key generation rate

In principle, BB84 protocol supports secure quantum communication by assuming transmitter and receiver devices to be ideal. However, practically it is very challenging to build an ideal single photon source and detector. These imperfections in practical devices (i.e., wavelength mismatch, full width at half maximum pulse width mismatch and different arrival times of photon) lead to side-channel attacks. In this work, we have analyzed the wavelength mismatch and pulse width mismatch issues associated with four laser-diode based practical BB84 transmitter. An asymptotically achievable rate for extraction of secure key (also known as key generation rate) is estimated from side-channel leakage calculation between transmitter (Alice) and adversary (Eve).