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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.)

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  • $\begingroup$ You may want to edit your title because it might seem that the ciphertext itself has no information. $\endgroup$
    – Patriot
    Oct 3, 2019 at 10:06
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    $\begingroup$ @Patriot I just did, thanks. Sometimes a little comma does the difference! $\endgroup$
    – Basj
    Oct 3, 2019 at 10:15
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    $\begingroup$ I know this rule @e-sushi, but please don't be so strict with it: this tool is so-crypto-specific, that if we ask this on softwarerecommendations.SE, far far less people will have knowledge in this niche, and therefore the chance to find good tools for doing cryptanalysis will be divided by a factor 10. For such specific tools, I think that "ask on softrec.SE instead" should be mitigated. $\endgroup$
    – Basj
    Oct 4, 2019 at 14:16
  • $\begingroup$ @Basj Killed my comment. I somewhat disagree about softwarerec being *that" useless for specialized tools, but since you got an answer that satisfied you, I sure don't want to be a party p00per. Instead, I'll join the +1 league. Have a nice weekend! o/ $\endgroup$
    – e-sushi
    Oct 5, 2019 at 15:21
  • $\begingroup$ Thanks for your comment :), have a nice week end too! $\endgroup$
    – Basj
    Oct 5, 2019 at 17:36

2 Answers 2

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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

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  • $\begingroup$ Really interesting tool, I've started to look at the UI of CT1. I've tried to crack this ciphertext 96==@O9@HO2C6OJ@FOE@52JnOH92EVDOFAnO?@E9:?8OC62==JO?6HO96C6] with no luck for now (a few english words crypted with ROT47, similar to ROT13). I tried Analysis > Symm. encrypt. > Ciphertext only > Vigenere or Substitution but then it's not really automatic and I haven't found the parameters that makes it work. But here it should be quite easy. Would you have an example of steps to do in Cryptool for a working cryptanalysis on a simple ROT47? $\endgroup$
    – Basj
    Oct 3, 2019 at 7:16
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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...)

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