I have got the following documents: (1) The plaintext (2) The ciphertext (3) The python program used to encrypt/decrypt the text

My goal is to find the key that was used to encrypt the plaintext into the ciphertext. I have tried using pkcrack on my MAC OSX machine (which took a few hours to run), however that failed and the key was not identified. I was thinking that there may be an alternate way considering I have the python code that was used to encrypt the text. For reference, it is not possible to brute force this key (well, at least not recommended)

Thank you!

  • 2
    $\begingroup$ We're gonna need to know the details of how the message was encrypted. Specifically the algorithm used, the key size, and the mode of operation (if a block cipher was used; this may or may not be applicable)... Although I have a feeling we're just gonna end up telling you it's impossible, we should at least know what we're saying is impossible first. $\endgroup$
    – Serpent27
    Oct 3, 2020 at 2:59
  • $\begingroup$ Encryption may be easier to crack with known plaintext, but that doesn’t mean it’s necessarily easy. $\endgroup$
    – gnasher729
    Oct 4, 2020 at 17:20
  • $\begingroup$ PKCrack is used only for the very-primitive cipher used in the original PKZip compression program ... and even then it's not very good. Much more successful attacks can be mounted against PKZip if the archive contains four or five members. $\endgroup$ Oct 5, 2020 at 15:22


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