To encrypt a message e.g. Relieve Baden Powell at Mafeking
- Pick a keyword without repeated letters – e.g. HEATONS
- Insert in a 5 x 5 square (combining I and J), starting with the key, continuing with the alphabet from A, again avoiding repetitions
- Write out the message in digraphs (2 letter groups), again avoiding repetitions by inserting Q, X, or Z. The choices make the code harder for opponents to crack. With both choices, for the sake of your allies, be consistent. Let’s use Z and I here:
re – li – ev – eb – ad – en – po – we – lz – la – tm – af – ek – in – gz
- To encrypt the message, use the three rules of Playfair Ciphers:
- Rectangles: Same rows, opposite corners
e.g. re becomes PT
- Columns: One down. On the bottom row, imagine an identical table underneath.
e.g. we becomes ES
- Rows: One right. At the end of the row, imagine a duplicate table to the right.
e.g. li becomes FK
Encryption: PT FK HW AS OB HS UE ES UO IO HR HI TG FB LW
To decode, go up instead of down and left instead of right – and for ends of rows and columns, imagine duplicate tables above and to the left of your Playfair grid.
JCC Gold Status Challenge
Can you crack this Playfair Cipher (again using the keyword HEATONS)?
XF KC TU XK DE MU DW
JCC Platinum Challenge
Can you solve the brand new PlayfairPuzzle ?