title: Recover AES IV if only key and plaintexts are known
body: <p>If I decrypt a ciphertext in AES-CBC mode and the decrypted plaintext of the first block does not match the original known plaintext, it is clear that the IV used for decryption does not match the IV used during encryption.</p>
  
  <p>Neither of the IVs used for encryption or decryption is known.</p>
  
  <p>If I knew the ciphertext, I could do the following to find the IV used during encryption (tried it and it works):</p>
  
  <ol>
  <li>Set IV=0</li>
  <li>x = decrypt(ciphertext, IV)</li>
  <li>originalIV = x xor originalPlaintext</li>
  </ol>
  
  <p>Is there a way to recover the IV that was used in the encryption, given I know the original plaintext (before encryption), the wrong plaintext after decryption and the key?</p>