How feasible is to brute force the ENCRYPTION key if you have

  • the clear-text message
  • the encrypted-version of the same message
  • you know that Rijandel is the encryption algorithm
  • you know that the salt is 2 bytes long

The attack you describe is called a "known-plaintext attack". It was commonly used to break older encryption schemes, most notably Enigma in the second world war.

AES/Rijndael is not susceptible to known-plaintext attacks.

Further reading:

Wikipedia: Known-plaintext attack

Why is AES resistant to known-plaintext attacks?

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  • $\begingroup$ Hi! thank you for your answer, but i don't want to break the decryption key! i want to break the encryption! this might seem contradictory but i just need to send encrypted info... $\endgroup$ – Leonardo Jun 27 '19 at 1:30
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    $\begingroup$ @Leonardo Rijndael (including AES) is a symmetric cipher, the decryption and encryption key are (must be) exactly the same. Also, there's no such thing as a "salt" in symmetric cryptography; the closest thing is an "IV" ("Initialization Vector") or "nonce" (number used once) and it wouldn't be two bytes long. Salts are used in key-derivation functions (which take a password or other secret, and turn it into a key), though. $\endgroup$ – CBHacking Jun 27 '19 at 4:22

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