Cardan Grille

Question 1

Answer

Cardan encryption uses another text (understandable or not) of which only a few letters are from the original text.

In practice, Cardan uses a mask, a grille in which some cells are opaque, others empty.

Example: Code DCODE with the mask XXXXXX_XXXXXX_XXX_X_XXXXX_XXXX where X is an opaque cell and _ an empty one.

Superimpose the mask cover, write the text in the empty boxes, remove this cover and fill the rest with random letters.

Example: DCODE is written in empty cells XXXXXXDXXXXXXCXXXOXDXXXXXEXXXX and it is possible to fill with letters like OZPCESDVIDGABCNTEOHDERXJXEMLUE

Question 2

Answer

Cardan decryption requires knowledge of the grille. The decrypted text appears by placing the cover on the text.

Example:

OESDVBCNEOHDEEML

XXX_XX_XX_X_X_XX

XXXDXXCXXOXDXEXX

___D__C__O_D_E__

Question 3

Answer

The ciphered message is very long compared to original plain text.

Question 4

Answer

The decryption without grille is very difficult, one should try all the grids.

Using a probable word, it is possible to estimate the coverage mask and know the amount of letters to ignore.

Cardan Grille Decoder