The invention provides a U disk (mobile hard disk)
encryption method which monitors the
USB Hey state in real time, carries out identity
verification and obtains a key by authorized
USB Key, wherein the protected U disk (mobile hard disk) is divided into a protective area and a non-protective area; the protective area is mapped into a virtual disk when the authorized
verification is passed, data wrote into the disk is encrypted and the data read from the disk is decrypted; the non-protective area is still used as a common U disk (mobile hard disk). When the
USB Key does not exist, the protective area cannot be accessed. The data stored in the protective area of the U disk (mobile hard disk) is encrypted forever, and is automatically decrypted in a memory when being used by a user. The invention supports the U disks (mobile hard disks) and file systems of all types, does not change the use
habit of conventional data and the action of application programs of users, and does not require the users to buy new U disk (mobile hard disk) equipment.