portable electronic storage devices with hardware based security are described . according to one exemplary embodiment of the present invention , a portable electronic storage device comprises a security engine integrated thereon . the security engine is configured to provide data encryption , data decryption , and encryption / decryption key generation according to a security standard ). aes is a symmetric encryption algorithm processing data in block of 128 bits . under the influence of a key , a 128 - bit data block is encrypted by transforming the data block in a unique way into a new data block of the same size . aes is symmetric sine the same key is used for encryption and the reverse transformation . the only secret necessary to keep for security is the key . aes may use different key - lengths .