Once you know that Q, for example, equals E, then that’s true for every Q in the problem. In the Playfair cipher, there are many letters that will stand for an E, making it much harder to crack!

The Double Playfair system is described in recently declassified documents in the National Archives. They were formerly MOST SECRET and were produced by Bletchley Park. Back to Double Playfair Cipher ...

In 1854, Sir Charles Wheatstone invented the cipher known as "Playfair," named for his friend Lyon Playfair, first Baron Playfair of St. Andrews, who popularized and promoted the cipher. Its ...