The Playfair cipher is a digraph substitution cipher. It employs a table where one letter of the alphabet is omitted, and the letters are arranged in a 5x5 grid.

(a) Using Playfair cipher, encrypt a plaintext "Cryptography is the practice of techniques for secure communication" with a key "PLAYFAIR". Remove the letter "J" from the alphabet.

(19 marks)

(b) Is there any drawback of Playfair cipher? Justify your answer.