Tool for decrypting / coding with the Tap code, it takes his name because it consists of transmitting coordinates in a letter grid by knocking/hitting things/a wall (or producing sounds)
Tap Code Cipher - dCode
Tag(s) : Substitution Cipher
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The tap code cipher uses a grid of letters, usually 5x5, containing 25 of the 26 letters of the alphabet (a letter is omitted, often the J, the K or the Z).
The coordinates (row, column) of the cells of the grid are numbered from 1 to 5 and thus any cell has an quivalent pair of digits (row, column)
Each character of the plain message must be present in the grid otherwise it can not be encoded.
The principle of the tap code is to strike a number of hits corresponding to the coordinates of each character.
Example: D in position 1,4 (line 1 column 4) corresponds to 1 then 4 shots and so DCODE translates to . .... . ... ... .... . .... . .....
The decryption of the tap code requires knowing the grid and counting the numbers of tap/knock by arranging them in groups of 2 forming the coordinates (line, column) of each letter of the plain message.
Example: To decode the message .... ..... . ... ....., count the dots (the taps): 4 4 1 1 3 5, rewrite in groups of 2 (4,4) (1,1) (3,5) and translate these coordinates into letters, respectively T,A,P, so TAP is the message in plain text.
The message is composed of a single character repeated between 1 and 5 times, a separator (like /) can be used, similar to the Morse.
The message can be in the form of a sound or a or light, again repetitive.
The name tap or knock is the onomatopoeia of the noise when the code is tapped or knocked on a surface such as a wall.
By default the grid is often the same: composed of the alphabet but without the letter K or the letter J (sometimes the letter Z), testing these few grids should be enough, otherwise to use a random grid and use the mono-alphabetic substitution decryption tool.
The grid may have a different size or use a shuffled alphabet.
A 6x6 grid containing 36 characters (26 letters and 10 digits) can be used to encode alphanumeric messages containing words and numbers.
Any communication containing 6, 7, 8 or more successive taps may indicate something special, a start of a message, an end of a message, a mistake made, etc.
The code is certainly very old, but there is no specific date. It has been used by prisoners in jails for centuries.
A little more recently, this code was used during the Vietnam War by a certain Captain Carlyle (Smitty) Harris.