COMPUTER FUNDAMENTALS

Detailed explanation-1: -It was used during the Second Boer War, and then in World War I and World War II (also by other countries). Like all other ciphers of that period, it was withdrawn from use when the first computers appeared. Nowadays, it can be broken relatively quickly by using brute force attacks.

Detailed explanation-2: -To decrypt the message, simply reverse the process: If the two letters are in different rows and columns, take the letters in the opposite corners of their rectangle. If they are in the same row, take the letters to the left. If they are in the same column, take the letters above each of them.

Detailed explanation-3: -The Playfair cipher is a written code or symmetric encryption technique that was the first substitution cipher used for the encryption of data. Introduced in 1854, it involved the use of keys that arrange alphabetical letters in geometric patterns in order to encode messages.

Detailed explanation-4: -Split the plaintext first into digraphs (pairs of two letters). Divide the plaintext into digraphs after that (pair of two letters). To identify the cipher (encryption) text, create a 5*5 key-matrix or key-table and fill it with alphabetic letters as follows: