Enter the text to be analyzed in the "ciphertext" box. Click "index
of coincidence" to compute the index of coincidence for the entire
text. To verify that breaking the ciphertext down into a number of
columns leads to monoalphabetic ciphers for each column, enter the
number of columns in the "period" box and click "test period". The
output shows the index of coincidence for each column graphically and
numerically.