Figure 4.

Decrypted images of lena, barbara, and house for the proper secret key (a–c), (d–f) decrypted images at $a=1.99999999999999,b=0.5,c=0.5,x_1\left(0\right)=0.11,x_2\left(0\right)=0.12$, and $k=0.87$, and (g–i) decrypted images at $a=2,b=0.5,c=0.49999999999999,x_{1,0}=0.11,x_{2,0}=0.12$, and $k=0.87$.