Abstract-With the advancement in the network transmission media, need for secure data communication is strongly felt. Recently fractal based cryptosystem has become a topic of active research in computer network system because of its chaotic behavior. The proposed method utilizes the intrinsic relationship between Mandelbrot function and Julia function to develop a nontransitional key cryptosystem. The process starts with the formation of public key using superior Mandelbrot set with the help of few global as well as secret parameters on both sides. After exchanging public keys, both parties will generate their own private key using superior Julia set which will be same on both sides. The method is also implemented for Ishikawa iterated fractal function and subsequently carried out detailed analysis for both functions. The given cryptosystem utilizing two different iteration methods and improve the performance by increasing the encryption key up to 128 bits. As per experimental result and performance analysis, the key has large key space, high key sensitivity due to chaotic nature and efficient execution time which helps to achieve a secure communication network environment for data transmission.