Embedded Linux-based USB Encryption Driver Design

With the widespread use of embedded devices, These devices provide users with avariety of services and experience，but also save a lot of user information. Once sensitiveinformation stored on the embedded device leaks, will be a huge loss to the user, especiallyin business intelligence and national security. How to protect important information frombeing stolen, becoming the urgent needs of individuals, businesses and countries. The currentUSB technology has a fast data transfer speeds, it is very convenient to read and write datathrough the USB interface. Security control data through the USB interface has a veryimportant practical significance.This paper focuses on the Linux mass storage device drivers and DES encryptionalgorithm, After a detailed analysis of its working principle and source, USB device driverhas been transformed, the driver layer can automatically encrypt or decrypt data through theUSB interface. An increase in the original of the bulk-only transport protocol based on theencryption and decryption modules to realize the data processing, The module plaintext datafor those derived from user space through the DES encryption algorithm, Finally, the ciphertext data to write to the USB storage device, When the user wants to read the USB storagedevice cipher text data, the module will automatically decrypt transmitted to the user space.In order to reduce the impact of encryption and decryption operations on systemperformance, now for some DES encryption algorithm has been optimized: Will separate outthe subkey generator, when USB device is inserted, first generate16subkeys, In order toavoid the back of the DES encryption algorithm iterates.After transformation, the mass storage device driver for file transfer experiments, theresults show that the driver cannot degrade system performance based on the data throughthe USB interface for effective security protection.