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Autoclave Cipher

Tool to decode AutoKey automatically. Autoclave cipher is a cryptographic system using the plaint text message as key, hence its other name: Autokey.

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Autoclave Cipher -

Tag(s) : Cryptography, Vigenere Variant

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# Autoclave Cipher

## Autoclave (Vigenere) Encoder

### Optional parameter

Tool to decode AutoKey automatically. Autoclave cipher is a cryptographic system using the plaint text message as key, hence its other name: Autokey.

### How to encrypt using Autoclave cipher

Encryption uses any algorithm using a key (most algorithms are compatible)

Autokey process can apply on many ciphering systems, it consists in replacing the key by key+message.

Example: If the algorithm is Vigenere, the key is KEY. To encrypt DCODE with Autoclave, the key becomes KEYDCODE.

The chosen algorithm is applied on plain text, changing the key modifies the ciphered message.

Example: The key is no more KEY but KEYDCODE, the message is not NGMNI but NGMGG.

### How to decrypt Autoclave cipher

Decryption requires to know the chosen algorithm and the initial key.

Example: Decrypt the ciphered message NGMGG (crypted with Vigenere Autokey) and the key KEY.

The decryption begins normally for known letters of the key.

Example: Decryption of NGM with the key KEY gives DCO (the first letters of the plain text).

Next deciphering steps uses as key the first plain letters.

Example: Decryption of the next letters GG with the first letters of the plain text DC as key gives DE. The plain text is DCODE.

### How to recognize an Autoclave ciphertext?

Using Autokey changes properties of the ciphertext, generally the index of coincidence is lower than a normal index for a given algorithm.

### How to decipher Autoclave without key?

No magic method, but testing all one-letter keys can be useful. Indeed, key length can be short, it will be completed with plain text.

dCode try to find all probable key length and try all letters in order to maximize the probability for the text to be decrypted. (Method suggested by LeSingeMalicieux)