Computer Science Journals
The information must be secure while transmission. Cryptography is one of the methods to attain security. Many classical cryptosystems are developed based on simple substitution. Hybrid cryptosystem using byte substitution and variable length sub key groups is a simple nonlinear algorithm but the cryptanalyst can find the length of each sub key group because the byte substitution is static and if the modulo prime number is small then byte substitution is limited to first few rows of S-box.