The repositioning numbers are used to rearrange the portions of the plaintext string (to form an intermediate string) and the substitution numbers are used to substitute portions of the intermediate string with encoded portions. Concepts extend to a corresponding method of decrypting a ciphertext ...
Substitution ciphers replace bits, characters, or character blocks in plaintext with alternate bits, characters, or character blocks to produce ciphertext. A classic example of a substitution cipher is one that Julius Caesar used: He substituted letters of the message with other letters from the sa...