Does AES/CBC really requires IV parameter?

Question

I am writing a simple app to encrypt my message using AES / CBC (mode). As my understanding CBC mode requires IV parameter but I don\'t know why my code work without IV para

Answer 1

When it is used without an IV, for certain types of ciphers including AES, it implicitly uses 0 IV. See Cipher class documentation.

The disadvantage of a null IV (or a deterministic IV) is that it is vulnerable to dictionary attacks. The requirement for IV is to prevent the same plain text block producing the same cipher text every time.