Substitution Cipher

The symmetric cryptography process incorporates two methods, a substitution cipher and an upper triangle method for encryption and decryption. $\underline{\textbf{Substitution Cipher:}}$ In this approach, the positional weights of individual letters of a word are taken (e.g., $A=1, B=2, C=3$ and $\text{so on}$), shown in Figure 1, and a value that is obtained from the key, is added to those we