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Chaocipher

Tool to decrypt/encrypt with Chao-cipher, a polyalphabetic encryption algorithm using two evolving disk alphabet at each step.

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Chaocipher -

Tag(s) : Cryptography,Poly-Alphabetic Cipher

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Chaocipher

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Chaocipher Decoder





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Chaocipher Encoder





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Tool to decrypt/encrypt with Chao-cipher, a polyalphabetic encryption algorithm using two evolving disk alphabet at each step.

Answers to Questions

How to encrypt using Chaocipher?

Encryption uses two rotating disks on which is written a custom alphabethref (originally the 26 letters from A to Z in any order).

The two disks are identical and linked with a kind of gearing (ratio 1:1), if one turns clockwise, the other turns anti-clockwise.

Let the two disks be
CHAOBDEFGIJKLMNPQRSTUVWXYZ for the LEFT disk (cipher text) and
CIPHERABDFGJKLMNOQSTUVWXYZ for the RIGHT disk (plain text) one wants to encrypt DCODE.

We call zenith the position 1 in each disk alphabet and nadir the opposite position on the disk, here 14.

For each letter to encrypt, one makes 3 steps :

First step : read the cipher letter corresponding to the plain letter (at the intersection of the two disks or at the same rank in the alphabets)

The plain letter D is in front of the cipher letter G.

Second step : make a special permutationhref of the LEFT disk. This operation is composed of 4 actions:

1. Make a rotation of the alphabet on order to set the cipher letter at the zenith (position 1)

The alphabet becomes GIJKLMNPQRSTUVWXYZCHAOBDEF

2. Extract the letterhref in position zenith+1 (on the right of zénith) and leave the position empty

One extracts I.
The alphabet becomes G.JKLMNPQRSTUVWXYZCHAOBDEF

3. Shift all letters from position zenith+2 until nadir (zenith+13) included by shiftinghref them on the left

The alphabet becomes GJKLMNPQRSTUV.WXYZCHAOBDEF

4. Insert the extracted letterhref at step 2 in the empty hole in position nadir (zenith+13)

The alphabet becomes GJKLMNPQRSTUVIWXYZCHAOBDEF

Third step : make a special permutationhref of the RIGHT disk. This operation is composed of 4 actions:

1. Make a rotation of the alphabet in order to set the letter immediately to the right of the plain letter to the zenith (the plain letter is in position zenith-1).

The alphabet becomes FGJKLMNOQSTUVWXYZCIPHERABD

2. Extract the letterhref in position zenith+2 and leave the position empty.

One extracts J.
The alphabet becomes FG.KLMNOQSTUVWXYZCIPHERABD

3. Shift all letters from position zenith+3 until nadir (zenith+13) included by shiftinghref them on the left

The alphabet becomes FGKLMNOQSTUVW.XYZCIPHERABD

4. Insert the extracted letterhref at step 3 in the empty hole in position nadir (zenith+13).

The alphabet becomes FGKLMNOQSTUVWJXYZCIPHERABD

After these steps, one gets the cipher message GZNDZ.

How to decrypt Chaocipher?

Decryption is identical to encryption with its 3 steps. Beware to read the plain letter on the right disk corresponding to the cipher letter on the left disk.

How to recognize Chaocipher ciphered text?

The ciphered message has a low index of coincidencehref, it is hardly distinguishable.

How to decipher Chaocipher without disks?

It is nearly impossible. However it the initial disk order has been defined using deranged alphabetshref, it is possible to some couples of keywords.

What are the variants of the Chaocipher cipher?

It is possible to change the size of the alphabet, or defining new positions for permutationshref of the alphabets.

When Chaocipher have been invented?

This ciphering has been invented by John F. Byrne in 1918.

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Source code

dCode retains ownership of the source code of the script Chaocipher. 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 Chaocipher script for offline use, for you, your company or association, see you on contact page !

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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 Chaocipher tool. Thank you.


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