The Output Feedback (OFB) mode is a typical block cipher mode of operation using block cipher algorithm. In this version, Data Encryption Standard (DES) and Advanced Encryption Standard (AES) processing ability are provided. The cipherkey length for DES should be 64 bits, and 128/192/256 bits for AES. Another limitation is that the working mode works on units of a fixed size (64 or 128 bits for 1 block), but text in the real world has a variety of lengths. So, the last block of the text provided to this primitive must be padded to 128 bits before encryption or decryption.