I have given the Initialization vector and the input text. Also I have the encoded text.
Now my problem is, how can I find the key, because my task is to change the output text. (its a homework and my prof said you can do it in an half hour in train on the way at home... but I have absolutely no idea and just know how AES and CBC works, but absolutely not how I have to start by this task.
The task: first 16 byte are the initialization vector and the second 16bytes are my ciphertext. And I have my text that is "Send 5$ to Carl". Now I THINK that I need first the key cause my task is to change the message "Send 5$ to Carl" to "Send 50$ to Bob.