  In this paper we investigate the security of continuous variable BB84 quantum
key distribution protocol using single photon added then subtracted squeezed
coherent state SPASSCS. It's found that the SPASSCS is a non-Gaussian and
nonclassical state. Its non-Gaussianity and non-classicality are exhibited via
the Wigner function. It's shown that the proposed state is generally robust
against the eavesdropping strategies, such as intercept-resend attack and
superior channel attack. Further, a comparative study has proved the strong
efficiency of the proposed state over coherent state, squeezed coherent state
and photon added then subtracted coherent state. Our analysis employs bit error
rate, mutual information, and secure key gain.
