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Polybius Cipher

Tool to decrypt/crypt Polybius automatically. Polybius cipher (or Polybius Square) consists in replacing each letter by its coordinates of its position in a grid (usually a square). This encryption system can be used with a key which generates a deranged alphabet to fill the grid.

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Polybius Cipher -

Tag(s) : Cryptography,Substitution Cipher

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Polybius Cipher

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Polybius Decoder








Polybius Encoder








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Tool to decrypt/crypt Polybius automatically. Polybius cipher (or Polybius Square) consists in replacing each letter by its coordinates of its position in a grid (usually a square). This encryption system can be used with a key which generates a deranged alphabet to fill the grid.

Answers to Questions

How to encrypt using Polybius cipher?

Encryption uses a 5x5 grid filled with letters.

One wants to crypt DCODE with the grid

\12345
1ABCDE
2FGHIJ
3KLMNO
4PQRST
5UVWXY
.

As latin alphabet has 26 letters, one has to choose a letter to remove, usually it's J, V, W or Z which are deleted (here the Z).

The order of the letters in the grid can be modified, often one uses a key to generate a deranged alphabethref.

The encryption phase is a substitution of each letter by its coordinates (line, column) in the grid.

D is located line 1, column 4, so coded 14; C is located line 1, column 3, it is coded 13.

The ciphered message is then 14,13,34,14,15

How to decrypt Polybius cipher?

Decryption requires to know the grid and consists in a simple substitution of couples of coordinates by the corresponding letter in the grid.

Let the message be 351332542114 to decrypt with the grid (created with DCODE as key and without letter J):

\12345
1DCOEA
2BFGHI
3KLMNP
4QRSTU
5VWXYZ

One splits the message in bigrams, couples of numbers are the coordinates of each plain text letter.

35,13,32,54,21,14, 35 stands for 3rd line, 5th column, so letter P, and so on.
The plain message is POLYBE.

How to recognize Polybius ciphered text?

The ciphered message is constituted of couples of coordinates (generally these are digits from 1 to 5) and so has an even number of characters.

Coordinates may have at most 25 distinct values.

How to decipher Polybius without the grid?

Polybius is in fact a simple substitution, one can replace each couple of coordinates by a random letter (there should be at most 25 distinct ones) and try a monoalphabetical desubstitutionhref.

What are the variants of the Polybius cipher?

It is possible to use a grid of another size, may be rectangular. It is also possible to use other coordinates notation, for example column or line name other than digits from 1 to 5, but also to note then in column-line rather than line-column.

The author (Polybius) had proposed to transmit coded messages remotely, for example, using torches. N in the right hand and M in the left hand for the coordinates N, M for example.

When Polybius Cipher have been invented?

The greek historian Polybius described it in 150 before JC.

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Source code

dCode retains ownership of the source code of the script Polybius Cipher. Except explicit open source licence (free / freeware), any algorithm, applet, software (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or any snippet or function (convert, solve, decrypt, encrypt, decipher, cipher, decode, code, translate) written in PHP (or Java, C#, Python, Javascript, etc.) which dCode owns rights can be transferred after sales quote. So if you need to download the Polybius Cipher script for offline use, for you, your company or association, see you on contact page !

Questions / Comments


Team dCode read all messages and answer them if you leave an email (not published). It is thanks to you that dCode has the best Polybius Cipher tool. Thank you.


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