5/19/2023 0 Comments Playfair cipher decoderIf you are interested in learning how the Playfair cipher works, Berkeley has a great explanation on their website.Below is a video from National Treasure 2: Book of Secrets, where they use a computer with a Playfair Decoder to break a message. 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. In rules 2 and 3 shift up and left instead of down and right. 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. The Playfair cipher is a polygraphic substitution cipher, meaning that it encrypts multiple letters at once. The resulting grid is used to encode and decode messages. The ciphertext above represents "SIR CHARLES WHEATSTONE" encrypted using the key PLAYFAIR.Throughout my upbringing, I often heard of detectives and spies using the Playfair cipher as a way to encode/decode messages’ meanings. The grid is filled with a keyword, and then the remaining letters of the alphabet are added in order, skipping any letters that appear in the keyword. Playfair ciphers, and variants of it, are occasionally used in CTFs, geocaching mystery caches, and logic puzzles. The Playfair cipher was used during World War I, but is no longer used by military forces since it can easily be broken by modern computers.See here for a more comprehensive description. If they are same letter, addĪ padding letter (for instance X) or pick the letters on row down and one step to the right. If they form a row, pick the letters one step to the right. If they form a column, pick the letters one row down. If they form a rectangle, pick letters from the same rows but other corners. The grid is formed by first taking a code word (with duplicate letters removed) and then adding any alphabet characters missing.Ī digraph is transformed by looking up the two characters in the grid.Since there are only 25 spots, one character has to be omitted (for instance J, which is replaced by I). A grid of 5x5 letters is used for encryption.This makes frequency analysis much harder, since there are around 600 combinations instead of 26. Instead of encrypting single letters, the Playfair cipher encrypts pairs of letter (digrams or bigrams).It was invented in 1854 by Charles Wheatstone, but named after lord Playfair after he promoted it heavily.It was the first practical polygraph substitution cipher in use. The Playfair cipher is a classic form of polygraphic substitution cipher.
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