Autoclave Cipher

Autoclave encryption uses a cryptographic algorithm with a key (all algorithms are not compatible).

The Autoclave principle consists in replacing the key by concatenating the key and the message (key + message).

Example: If the key is SECRET. To encode AUTOCLAVE with Autoclave, code normally with the chosen algorithm but with the key SECRETAUTOCLAVE.

Apply the selected algorithm to the plain text: the key self changes the encrypted message.

Example: The key is no longer SECRET but SECRETAUTOCLAVE, the message encrypted by Vigenere is no longer SYVFGESZG but SYVFGEAPX.

The size of the initial key must be smaller than the text size for the autoclave to work.

Autoclave decryption requires to know the chosen algorithm and the initial key.

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

The decryption begins normally for known letters of the key.

Example: Decryption of SYVFGE with the key SECRET gives AUTOCL (the first letters of the plain text).

Next deciphering steps uses as key the first plain letters.

Example: Decryption of the next letters APX with the first letters of the plain text AUT as key gives AVE. The plain text is AUTOCLAVE.

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

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 offers a bruteforce mode that tries to find the probable length of the key, by testing different lengths of key word. For each letter, dCode attempts to maximize the probability that the text will be plain by frequency analysis. (Method suggested by LeSingeMalicieux)

Autoclave is the name of an industrial device that makes it possible to expose elements to high pressures and temperatures.

Autoclave is the name of a rock band and the name of an album of that same band.