Playfair Cipher Confusion with one column encryption Recently I decided to learn "Playfair Cipher", and I have hit a road block.
what do i substitute the letters for if they are on the same column? Here is an example:

CIADX
BEFGH
KLMNO
PQRST
UVWYZ


With the Key being CIAD  (Random Text)

I want to spell the word "trust" but I do not know what rule to follow for the T &amp; R. I would really appreciate help on this. TIA
TR would be replaced using rule 2 of the Wikipedia description:


  If the letters appear on the same row of your table, replace them with the letters to their immediate right respectively (wrapping around to the left side of the row if a letter in the original pair was on the right side of the row).


So TR would become PS. See also step 10 of the example there.

Note that T and R are on the same row, not the same column.

You may want to use a larger key (i.e. one that includes more characters of the alphabet).