COMPUTER NETWORKING

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 Like all other ciphers of that period, it was withdrawn from use when the first computers appeared.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 uses a 5×5 grid of letters, and encrypts a message by breaking the text into pairs of letters and swapping them according to their positions in a rectangle within that grid: “HI” becomes “BM".