Encrypt given data using des-cfb cipher algo. DES in CFB (Cipher Feedback) mode, a mode that allows for encryption of smaller blocks of data. CFB mode was introduced to make DES more versatile in handling variable-length data. While CFB provides better security than ECB, DES itself is still considered insecure due to its 56-bit key length. Our encryption process prepends the IV string used during the encryption process in the encrypted data so that it can be used during decryption.