The encrypted message is therefore 'DQBDAXDQPDQH'.ĭecryption can be achieved by simply reversing these steps.
The message is first converted to its x, y coordinates, but they are written vertically beneath.ġ 4 4 1 1 2 1 4 1 1 5 3 1 4 4 1 3 5 1 4 4 1 2 3įinally, they are divided up into pairs which are used to look up the encrypted letters in the square. We use this archetypal Polybius square where I and J share the same position. Suppose we want to encrypt the message 'ATTACKATDAWN'. Any 5 x 5 Polybius square can be used but, as it only has 25 cells and there are 26 letters of the (English) alphabet, one cell needs to represent two letters - I and J being a common choice. It uses a 5 x 5 Polybius square combined with transposition and fractionation to encrypt a message. The Bifid cipher is a polygraphic substitution cipher which was invented by Félix Delastelle in around 1901. You are encouraged to solve this task according to the task description, using any language you may know.
