Encrypt given data using aes-256-ofb cipher algo. AES with 256-bit key in OFB (Output Feedback) mode, which turns a block cipher into a stream cipher. OFB mode was developed to address some weaknesses of ECB mode by making encryption dependent on previous outputs. Secure but vulnerable to bit-flipping attacks. Rarely used today. Our encryption process prepends the IV string used during the encryption process in the encrypted data so that it can be used during decryption.