The secret key can be made by filling the first and part of the second row of a matrix with the word MORNING. Filling of rest of the matrix can be done using remaining alphabets. Consider alphabets Y and Z together in one cell of matrix. -

i. Secret Key = MORNING

ii. Plaintext = attack cancelled on Monday wait for next message

iii. Considering Y and Z in one cell matrix

iv. The playfair cipher matrix is as follows:

v. Dividing the plain text into blocks:

at ta ck ca nc el le do nm on …