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Let's say I receive a 1 MB encrypted file, but I get no information about the encryption method, and no password.

The only thing I can guess is that the person probably used a weak encryption method on a text file.

Are there ready-to-use software that will perform automatically a huge number of attacks on the ciphertext, from the simplest methods to the most complicated?

i.e. it would start with ROT13 / Vigenere, frequency analysis, etc., then Hill cipher or other easy-to-crack methods, then RC4 (I read in many places it is considered as weak, but I still don't know if one can easily break it if I don't give any other information than just the ciphertext), etc. and it would stop if some text is found (let's say at least 20% of the words are in a big dictionary)

(I can imagine such software would be used by intelligence agencies, etc. because it would speed up decryption.)

Basj
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2 Answers2

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The project Cryptool does some if not all of what you want. I have not used it extensively, but it seems quite well documented. Below from the webpage:

  • CrypTool 1 (CT1) was the first version of CrypTool. It was released in 1998 and allows to experiment with different cryptographic algorithms. CT1 runs under Windows and has two successors: CT2 and JCT.

  • CrypTool 2 (CT2) supports visual programming and execution of cascades of cryptographic procedures. CT2 contains an especially large number of cryptanalysis methods and also runs under Windows.

  • JCrypTool (JCT) is platform-independent and runs under Linux, Mac and Windows. One focus are post-quantum (signature) algorithms.

  • CrypTool-Online (CTO) was released in spring 2009. Here you can try out in a browser (on a PC or a smartphone) different algorithms.

The current version of CrypTool 1 offers numerous classic and modern cryptographic algorithms (encryption and decryption, key generation, secure passwords, authentication, secure protocols, etc.)

Visualization of several algorithms (Caesar, Enigma, RSA, Diffie-Hellman, digital signatures, AES, etc.)

Cryptanalysis of several algorithms (Vigenère, RSA, AES, etc.)

Cryptanalytical measurement methods (entropy, n-grams, autocorrelation, etc.)

Related auxiliary methods (primality tests, factorization, base64 encoding, etc.)

Number theory tutorial

Comprehensive online help

Basj
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kodlu
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1

The other answer about CrypTool led me after some links to the freeware CryptoCrack, which seems to be a great tool.

Here is how to use it on a simple example (taken from the documentation):

  • Paste LZXLDCRX FEVLZK XVJJSRCI LGZ XDCLRCZCLK BRIJVLZ DOZJ LGZ ZVJLG’K KNJMVXZ V MZP RCXGZK FZJ SZVJ, VWDNL LGZ KVBZ KFZZY LGVL V MRCIZJCVRE IJDPK. in the Cipher text field

  • Click in another input field, it will update the frequency analysis

  • Click on Solve cipher (green tick button), it will show the most probable Cipher

  • Choose one cipher in the dropdown list, example: Aristocrat, then Solve cipher again!

  • It will find the plain text !

Note: I had no luck with 96==@O9@HO2C6OJ@FOE@52JnOH92EVDOFAnO?@E9:?8OC62==JO?6HO96C6] (a few words into ROT47) because the @ couldn't stay in the Cipher text field (even if I uncheck 26-letter alphabet in the options...)

Basj
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