I came across a problem very similar recently and wondered if anyone knew how to solve this.

So say for example I have an RAR archive called archiveA.rar and a password to protect it the password is known as keyA. keyA is stored on the server but I can send the server any file and it will compress it into a RAR file and encrypt it with keyA. I can keep sending files to the server to retrieve encrypted versions of different files. So my question is with all this given information and the fact that I can send unlimited files to the server can I solve for keyA, if so please explain how I would do so?

  • Could you explain why are you asking specifically about RAR?
    – techraf
    Mar 22, 2016 at 6:52
  • Because the scenario I was in recently was dealing with a RAR, and I can't seem to find any resources on how RAR files are encrypted.
    – munim_R
    Mar 22, 2016 at 6:54

1 Answer 1


RAR uses AES256 for encryptionsource, thus the question is whether AES is cryptographically resistant to a known-plaintext attack.

At present there is no known method that allows retrieving AES encryption key given unlimited number of plaintext inputs and corresponding outputs faster than brute-force. Although there is no proof that it is impossible.

See related posts on Cryptography SE.

  • thanks a bunch for helping me understand this concept :)
    – munim_R
    Mar 22, 2016 at 7:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.