Grille (cryptography)

When Fleißnerschen template also Fleißnerschen table is an encryption method in which by transposition using a template of the plain text of a message to a ciphertext is scrambled. The Fleißnersche template is named after the Austrian Colonel Eduard Fleißner of Wostrowitz. This had the procedure in 1881 published his treatise in new cartridges secret writing. The French writer Jules Verne described the encryption process with the Fleißnerschen template 1885 in his novel Mathias Sandorf.

The procedure

The Fleißnersche template consists of a cardboard square, from which several smaller squares are cut out. The template is placed on a sheet of paper and each one letter of the plaintext is entered in a cut-out square. Then the template is rotated ninety degrees and the following letters are entered in the gaps. The whole thing takes place four times, so that a square is created with the scrambled letters. If the message is longer, a new square is started. If it is shorter, the remaining gaps with randomly chosen letters are filled.

Example

Clockwise rotation (clockwise) results in the following scheme:

In turn left ( counterclockwise) results in the following scheme:

Mathematical Foundations

Conditions for the production of such templates are:

  • The number of total fields is divisible by 4 ( the template is applied four times )
  • A quarter of the fields is cut
  • No symmetry within the cut fields

In this specific case, the template has 36 fields, of which 9 are cut.

Generate can be the template by filling example, a quarter of the matrix with the values ​​1 to 4, and three times this turns into the next quadrant under cyclic shift of the digits by 90 °. Be Cut out all fields with the same digit, eg If one of the first uniform distribution over all four quadrants of the number of such possible templates yields the following statement:

Words, there are 181440 possible templates, although not all are well suited because fields often lie side by side and the text is so readable.

For templates in any sizes following formula can apply with uniform distribution:

With a number of fields

Transposition cipher France
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