(a) Secret key rate under Gaussian collective attack with symmetric configuration. (b) Secret key rate under collective Gaussian attack with asymmetric configuration. (c) Secret key rate under coherent attack with symmetric configuration. (d) Secret key rate under coherent attack with asymmetric configuration. In the asymmetric configuration, the entangled source is placed near Alice with T₁ = 0.99. For the coherent attack, the value of g is − ( ω 1 − 1 ) ( ω 2 + 1 ) . The blue line, orange line and red line represent the block lengths of N = 10⁴, 10⁵ and ∞, respectively. The modulation variance V is 10, the reconciliation efficiency is 0.95, the theoretical excess noise is set as 1.1, the security parameter ε is set as 10⁻¹⁰, and η = n/N = 0.5.