1. Introduction XTS-AES (XEX Tweakable Block Cipher with Ciphertext Stealing, using AES) is a mode of operation for block ciphers. It is specifically designed for disk encryption and storage device encryption , where data is organized into fixed-size blocks (sectors). The "128" in XTS-AES-128 indicates that the underlying AES cipher uses a 128-bit key , resulting in a total key length of 256 bits (explained below).