With the sophistication of digital encryption, the Playfair cipher was not an acceptable form of encoding messages, because a computer could solve Playfair ciphers in a matter of seconds. Once computers were invented and used to break codes, the Playfair cipher was no longer used. The Playfair cipher was popular because it was complex enough to throw off cryptographers, but didn’t require any special tools or equipment to solve. Other countries–Australia, Germany, and New Zealand–would use the Playfair cipher in the 1940’s. The Playfair cipher was predominantly used by British forces during the Second Boer War (1899-1902) and World War I (1914-1918). Once Wheatstone established that with proper training even school children could properly use the Playfair cipher, Britain would make the Playfair cipher their prominent tool to encrypt secret, but non-critical information in the battlefields. The Playfair cipher was originally thought by the British Foreign Office as too complex they feared that using this cipher would take too much time and would be ineffective in the field. Instead of a twenty-six possible monograms, with a digraph there are six-hundred possibilities. This is important because it makes breaking messages much, much harder. The Playfair cipher is notable because it is one of the first ciphers that paired letters (also known as a digraph) instead of using a single letter cipher. The Playfair cipher– which if you think about it, you REALLY are not “playing fair” if you are using a cipher, now are you?–was created by Charles Wheatstone, an English scientist and inventor, in 1854. I was always curious as to how this cipher worked–and of course the history behind it–so I looked it up.

If there is an odd number of letters, a Z is added to the last letter.Throughout my upbringing, I often heard of detectives and spies using the Playfair cipher as a way to encode/decode messages’ meanings.

The plain text is split into pairs of two letters (digraphs).

The initial alphabets in the key square are the unique alphabets of the key in the order in which they appear followed by the remaining letters of the alphabet in order.

If the plaintext contains J, then it is replaced by I. However, its not resistent to all forms of cryptanalysis. The Playfair Cipher is a simple pencil-and-paper cipher which doesnt suffer from some of the common weaknesses with simple substitution ciphers. Each of the 25 alphabets must be unique and one letter of the alphabet (usually J) is omitted from the table (as the table can hold only 25 alphabets). The Playfair Cipher tool is a Chrome Packaged App for quickly encrypting and decrypting plain text with the Playfair Cipher.

The key square is a 5×5 grid of alphabets that acts as the key for encrypting the plaintext.

The Playfair Cipher Encryption Algorithm: The Algorithm consists of 2 steps: The only difference is that it encryptsĪ digraph (a pair of two letters) instead of a single letter. Playfair cipher is an encryption algorithm to encrypt or encode a message.

The receiver of the plain text has the same key and can create the same key-table that is used to decrypt the message. For decryption the cipher is symmetric (move left along rows and up along columns). The decryption procedure is the same as encryption but the steps are applied in reverse order.