You can reach this dialog via the menu entry Analysis \ Symmetric Encryption (classic) \ Manual Analysis \ Playfair.
The analysis tool for the Playfair algorithm supports the manual analysis of a text encrypted with the Playfair algorithm. As a pre-condition, parts of the plain text must be available in addition to the cipher text. Based on this information the key matrix can be constructed.
Using intermediate results the matrix can be guessed or CrypTool can be asked for a suggestion. You can watch the results closely, correct them if necessary and finally try a decryption.
The encryption matrix can be edited via the fields Password and Matrix. An entry in the Password field is written to the matrix, as described in Playfair encryption algorithm. A character entered directly into the matrix exchanges the positions of the entered character with the character at the cursor, if the character at the cursor is not a star (‘*‚).
The activated option Update expected plaintext using the key matrix will make that after each re-computation of the key matrix the plaintext of the actualised decryption is displayed on the input line expected plaintext.
The text displayed in the box labelled Analysis result reflects the effect of the selected matrix.
The constraints for the matrix are shown in the field `Letter information´. This information is computed from the encrypted text and the assumed stipulation. They have no direct impact to the shown matrix, but give you some hints for suggesting the right encryption matrix.
The table Letter information displays the following information for all letters in the alphabet based on the content of the field `Expected plaintext´:
Hint: Normally letters which are listed in ‘row or col‚ but not in ‘horizontal‚ are often in the same column as the given letter.
Clicking the button `Create matrix´ suggest a matrix, which respects the constraints and therefore the stipulation based on the cipher text. The resulting matrix can be modified. Please note that changes to the matrix get lost, if you click on the button.
In the case that your stipulation does not begin on the first position or contains gaps you can put in a placeholder (‘*‚) by typing the space bar. CrypTool ignores all di-grams which contains at least one star in the stipulation.
When you type the stipulation, CrypTool can detect inconsistencies during the calculation for the constraints. The most common error is to type the same letter into the stipulation as the letter occurring in the encrypted text on the same position. Using the Playfair algorithm you can‚t get a letter for encrypting for itself. (An ‘A‚ will never be encrypted to an ‘A‚.)
The possible stipulation errors are:
The letter graph for the constrains contains several lists. By using a 5x5 matrix there could be only 4 letters in the same row of the key matrix. (Letters shown with an ‘!‘). If the calculation of the constrain comes to an result that 5 letters have to be in the same row, this list is exhausted. In the list 'row or col' this message occurs on the 9th letter.
In this case one of the neighbours was already calculated and the following calculation has the result that another letter has to be on this place.
Finally, the Button Output results of analysis uses the current key matrix to decrypt the cipher text and creates a new document window from the result. It also closes the dialog.