# Alter plaintext in block cipher AES in CBC mode

How can I alter the plaintext before decryption by changing the IV?

I know what the value of the plaintext should be. I also know the value of the IV (initial vector). The IV and the AES block are both 16 bytes long.

What I am trying to do is change what the plaintext will be into something meaningful. "SEND ME THE DATA ENCRYPTED" is the plaintext and "8f6f27b5dbfa2ba8367262bda7154d95" is IV.

I want to change the word "ENCRYPTED". I can change everything before using by changing the IV it but I cannot change it.

This the message encrypted:

IV: 8f6f27b5dbfa2ba8367262bda7154d95
CT: 798e0ff8b06cc27c1591a4088531a64a9b76a9be87a3e944c6e7000f24f5b9f9


So if you consider ASCII encoding you have two plain text blocks: "SEND ME THE DATA" and " ENCRYPTED" + padding (which we will ignore). Note the space before "ENCRYPTED".
IV: 8f6f27b5dbfa2ba8367262bda7154d95