Modification Affine Cipher Transform Digraph to Squared the value of ‘n’ in Text Security

Affine Cipher is the development of Classic Caesar cipher that multiplies plain text before shifting operation. Affine cipher has two parameters namely key a, and b. Key ‘a’ is multiplies the plain text. It must have an inverse with Great Common Divisor (GCD) from the number of characters. The Problems of Affine Cipher Algorithm is the number of characters available and the least possible of key ‘a’ that can be used, so it is considered to be a classic technique that is easy to hack. Generally, Affine Cipher is used to encrypt the plaintext of character ‘A to Z’ so that the number of keys ‘a’ is only 12 digits from 26 digits (n) is available. Development of affine had increased the key ‘a’ into 128 of 256 digits (n) with 8 bit of ASCII. Digraph Transform is the modification of text encryption. It able to square the value of n. Usually, Text is encrypted by one character. In Digraph Transform, text is encrypted by two characters. For two characters, multiplying integer of the first character by number of characters, then add integer of the second character.