Tool to decrypt/encrypt unsing the Nihilist cipher. The Nihilist Cipher is a variant of Polybius square, since it is a super-encryption of it.
Nihilist Cipher - dCode
Tag(s) : Substitution Cipher
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The Nihilist cipher is an over-encryption of the Polybius square. It uses a grid (usually 5x5 = 25 cells) that is filled with letters of the alphabet (often a deranged alphabet). For a 5x5 grid and the 26-letter latin alphabet, choose a letter to omit, often the J, V or W are omitted. The grid has digit headers for its rows and columns (typically 1 to 5).
To encrypt a text, it is necessary to replace each letter of the initial text, by its coordinates in the grid. Generally, the coordinates [row, column] (and more rarely [column, line]) are used. A numerical code consisting of pairs of digits is obtained.
Example: A is therefore coded 11 (because in row 1, column 1), E becomes 15 (row 1, column 5).
Example: The message to be encrypted: KREMLIN, which is therefore encoded 31,43,15,33,32,24,34
The particularity of the Nihilist cipher in relation to the Polybius cipher is its over-encryption. The nihilists use a key that is added for each couple of digits previously created.
The result of the addition is theoretically between 22 and 110. There are 2 ways of writing the result, either by separating the numbers (a space or a comma), or by concatenating them, in this way, for the 3-digits numbers keep only the last 2 digits (subtract 100 from sums that would be greater than 100).
Example: The key VODKA, which is coded 52,35,14,31,11, is added (value after value) to the encrypted text.
|Coded (Message) Letters||31||43||15||33||32||24||34|
|Coded (Key) Letters||52||35||14||31||11||52||35|
|Final Message (Addition)||83||78||29||64||43||76||69|
Example: The final encrypted message is 83782964437669
Decryption requires to know the grid and the over-encryption key.
The message can have the form of a list of numbers (2 or 3 digits) or of a large series of digits, in the second case, separate them into pairs of 2 digits.
Example: The encrypted message 577066392880, the key CODE and the grid
To decrypt, the coded key is subtracted from each pair of 2 digits and each number obtained is replaced by the corresponding letter with these coordinates in the grid.
Example: The key CODE is coded with the grid 13,35,14,15, it is then subtracted from the message:
|Coded Key (repeated)||13||35||14||15||13||35|
|Letter in the Grid||S||O||V||I||E||T|
Example: The plain message is SOVIET.
In the general case of using a 5x5 grid with coordinates from 1 to 5, the message is composed of numbers with the following properties:
- If the encryption is without a separator, the numbers are between 00 and 99 and the message is composed of an even number of digits.
- If the encryption is with separating spaces, the numbers are between 22 and 110
- In all cases, the numbers 11,12,13,14,15,16,17,18,19,20,21,31,41,51,61,71,81,91 can never appear by addition because they contain only one ten or only one unit.
Any reference to Russia (USSR), tsars or Russians traditions is a clue.
The word nihilist is generally associated with a philisophic doctrine, but in Russian the word нигилизм has a Latin root meaning nothing.
It is possible to make several variants:
- Inversion of coordinates: rather than using [row, column], it is possible to use [column,row].
- Change of coordinates names: the digits from 1 to 5 can very well be mixed or replaced by other digits.
- Multiple keys, it is possible to use several keys, summed successively, but this only extends the process time and does not complicate a brute-force attack.
The Russian nihilist movement is described in the history textbooks as between 1855 and 1885.