20IO International Conference on Information, Networking and Automation (ICINA)

Application of AES Algorithm in Digital Cinema Projection System Based on Da Vinci Technology

Xue-liang Wang College of information science and technology

Heilongjiang University Harbin, China, 150080

wxljsj@163.com

Fu-hai Xiao College of Information and Communication

Harbin Engineering University Harbin, China, 150001

xiaofuhai@hrbeu.edu.cn

Da-yong Wang Flight Simulation Institute of Airforce in Harbin

Harbin, China, 150001 9I5I985@qq.com

Abstract-To solve the security issues of digital cinema projection equipments, and avoid video data to be illegal theft or malicious tampering, this paper proposes a new type of design for encrypting digital movies using advanced symmetric encryption algorithm - AES128 with TMS320DM6446 and DaVinci technology. The project takes full advantage of the characteristics of high efficiency and programming flexibility of DaVinci processor, through allocating internal and external resources of the processor chip rationally, and using the DMA,

it only needs a small overhead to make digital movies protected. Meanwhile, for the strategies of different applications, this paper also gives encryption methods of different security levels. The test results show digital movies encrypted by AES128 can not play normally, which ensures the security of digital movies. The technology and methods adopted in the system are practical and worthy of using abroad.

Keywords-DaVinci Technology; AES128; Digital Cinema; Security; DMA

I. INTRODUCTION

Digital cinema is the high-tech products, which was born in the 20th century 80's. The production and storage of digital cinema is with digital technology and equipment, and it is delivered via physical media, such as satellite, fiber, disk and CD-ROM. Digital signals are reduced to video and audio which meet the film technical standards, and shown on the screen. Compared with traditional cinema, digital cinema is more vulnerable to theft, tampering and play in the process of transport and projection [1].

Therefore, it needs to adapt certain security mechanisms to protect the knowledge copyright of digital film programs not to be affected by the infringement in the digital cinema projection system. On August 2007, Technical Requirements of Digital Cinema Projection System has been published by the State Administration of Radio Film and Television, which specifies that digital movie is compressed by the encoding method of MPEG-2, and protected using the encryption algorithm of AESI28. In view of the above actual situation, this paper studies the project of AES 128 advanced symmetric encryption algorithm in digital film of MPEG-2 and its implementation methods, based on the hardware

platform of Da Vinci system, using Da Vinci software technique, meanwhile, for the strategies of different applications, gives encryption methods of different security levels.

The remainder of this paper is organized as follows: In Section II, the description of AES encryption algorithm is given. In Section III, the encryption design scheme of digital cinema projection system is presented. Section IV illustrates the experimental results. Finally, the conclusions are drawn in Section V.

II. DESCRIPTION OF AES ENCRYPTION ALGORITHM

The AES algorithm is a symmetric encryption algorithm, whose encryption key is equivalent to the decryption key. Under normal circumstances, the encryption speed of AES is 1000 times than non-symmetric encryption algorithm. AES is mainly applied to long plain text, such as file encryption, network encryption, database encryption, etc. The group length, key length and the number of encryption layer are available; group length and key length support 128bit, 192bit and 256bit; the length of group and key can be changed, which is determined by the encryption level[2].

The encryption and decryption of AES algorithm both use a mechanism of round transformation [3], which is composed of 4 parts: SubByte, ShiftRow, MixColumn and AddRoundKey. Among, SubByte is the replacement of Sbox, which uses Sbox to replace each byte of the state. The first 4 -bit and later 4-bit of each byte specifY the line and column of Sbox separately, and then take out the corresponding row and column elements in the Sbox as the output instead of the bytes. ShiftRow is a cyclic shift for different state by different offset, if each line counts from 0 positions, then the Oth line maintains invariable, and the 1 � 3rd line move to the right by the step of C 1 �C3 byte separately. The size of C1�C3 depends on the group of plain text (Nb). MixColumn is a linear transformation from column to column. AddRoundKey is the logical operation which XOR the results of MixColumn and sub-keys by byte.

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2010 International Conference on Information, Networking and Automation (ICINA)

III. ENCRYPTION DESIGN SCHEME OF DIGITAL CINEMA

PROJECTION SYSTEM

A. DaVinci Technique DaVinci technology is content-rich and complex, which

is released by TI Corporation recently. DaVinci technology is the set of system solutions and components, based on DSP, for digital multimedia applications, which provides integrated processors, software and tools [4], [S].The realization of AESI28 encryption algorithm in digital cinema projection system is just based on the system frame of DaVinci, using the rich system programming interfaces (SPIs), application programming interfaces(APIs) and over a thousand kinds of algorithm components to simplifY the design and accelerate the innovation of products, and to ensure that the products of design with high reliability and stability.

B. Hardware Design The realization of digital cinema projection system is

mainly based on the digital media processor of dual-core TMS320DM6446.TMS320DM6446 is a highly integrated video processing chip, which was released by TI Company in December, 200S, and called (DaVinci) digital media system on Chip (DMSoC) by the industry. The functional block diagram of TMS320DM6446 is shown as Fig.1 [6].

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Figure I. Hardware block diagram

As is shown in the Fig.l, DMSoC (digital media system on chip) include ARM subsystem, DSP subsystem, video processing subsystem (VPSS), system control modules, power management modules, external memory interfaces, external control modules and switching center resources (SCR) and so on.

ARM subsystem is mainly responsible for the overall configuration and system function control module of DM6446, Calling the video algorithms. DSP subsystem is responsible for the implementation of video algorithms,

whose operating frequency is close to 600MHz.The maximum of processing capacity of DSP-side can reach 4800MIPS, which enhances audio and video decoding capabilities greatly. Dedicated audio and video processors are used for the data processing. Video processing subsystem (VPSS) includes a video front-end input interface (VPFE) and a video terminal output interface (VPBE).The VPFE is used for capturing video signals, the VPBE outputs the image to the OSD. Through the SCR, DM6446 is realized to control the external modules and communication with them.

Through the asynchronous external memory interface (EMIF), this system links with a 64MB of NAND Flash, which stores the booting code and data, in order to boot and loader ARM Linux operating system. Through the AT A controller interface, the system links with a 160G of hard drive, for storing a lot of video files. DDR2 SDRAM is used to the buffer of video input image data, and storages ARM and DSP code.

C. Software Design When we encrypt the digital video with AES 128

encryption algorithm, considering the security of encryption, real-time and hardware resources overall, we adopt selective encrypted way, discarding the traditional way of full encryption, which regards MPEG-2 bit stream as the ordinary binary data, and uses the encryption way of encrypting each bit, not considering the coding structure of MPEG-2. The encryption way of selective takes full account of the coding structure of MPEG-2 [7], [8], which reduces the amount of encryption data, and satisfies the requirements of real-time of MPEG-2 video. The primary theory of algorithm mainly bases on the correlation of time and space of I, P, B frame in the frame structure of MPEG-2 to guarantee the security of video sequence encrypted.

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Through analyzing the layer structure of video stream of MPEG-2, we can know that the layer structure of MPEG-2 includes 6 parts: Video Sequence Layer, Group of Pictures Layer, Picture Layer, Slice Layer, Macroblock Layer and Block Layer. While I, P, B frame of the video sequence locate on the Picture Layer, which is the most important part of whole video sequence, and contains the actual video data. Therefore, the study of encryption is primarily in the Picture Layer.

Through analyzing a video stream of MPEG-2, whose size is lAM, we discover that the first frame (1) appears in the location of Sk, behind the I frame, there are multiple P and B in tum, and in front of the first I frame, there are the head information of video sequence and image group, which indicates the format of the video sequence, etc. In order to reduce the amount of video data that is encrypted, we use the DMA mechanism DaVinci software provides, by using ACPY3 function, bypassing the CPU, moving the video data in the background. When the DMA has processed IK data at a time, the variable of Count is added I. When the variable of Count is equal to S, we start to encrypt the data of I, P, B frame, using AES 128 encryption algorithm. The encryption round constant is 10, the length of group of plaintext and key is 4. We can decrypt the ciphertext that is encrypted to obtain original video stream, using AES 128 decryption algorithm.

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The flow chart of software of AES 128 encryption and

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Figure 2. Flow chart of AES 128 encryption and decryption algorithm

The entire software development is completed in the environment of Linux system, The ARM side of dual-core processors is responsible for the system call, and OSP side is responsible for the implementation of AES 128 encryption and decryption algorithm. In order to enable ARM core to calling the algorithms that implement on OSP core, we must package the algorithm of AES128 encryption and decryption into Codec Server managed by Codec Engine. In the * .tcf configuration file of Codec Server, we manage hardware resources of TM3200M6446 by setting OSP/BIOS. After repeated testing, we can obtain the optimal allocation situation of memory: for 80K LID of OSP core of TM3200M6446, 32K is configured into Cache, and the left 48K is as internal RAM; for 64K L2 of OSP core, 32K is configured into Cache, and the left 32K is as internal RAM.

At the same time, when we compile the Codec Server, through setting the optimizing profile as "-03" in package. bId of Co dec server, to optimize the code, and improve the efficiency of the implementation of the code.

IV. TEST RESULTS

The software development of this system is under the Linux operating system of the virtual machine, the version of Linux operating system: Monta Vista Linux Professional Edition v4.

Before the test, we use a cross cable to link the hardware platform with the host through a switch, and configure the NFS network services, in order to make the development board and the host can access each other. Meanwhile, in the Windows environment of the host, we use a serial cable to connect development board with the host, and set the HyperTerminal. Using the terminal, we can monitor the hardware system starting, and set the command parameters.

In practical tests, we found that If we only encrypted I frames of each video sequence, because of the relationship of time and space among frames, as well as I Blocks of P, B frames not been encrypted, the results of encryption is not very perfect, video sequences are still partially visible; when all I frames and I Blocks of P, B frames in the video sequences were encrypted, we could obtain better encrypted results; and when the video sequence data was encrypted completely, though we could get the highest security, because of needing to process most of the data, time consuming was the most.

In the testing process, we input the encryption commands in the HyperTerminal. The hardware system parses the commands by MSP430, reads the audio and video data stored in the HDO (hard disk), displays the films encrypted on the OSO. Figure3, Figure 4, Figure 5 are respectively the encryption image of encrypting I frames of each video sequence only, I frames and I Blocks of P, B frame, all I, P, B frames of digital movie. When we decode the encryption image, the input encryption video image can not play normally. Figure6 is the original video image, using AES 128 decryption algorithm.

Figure 3. Encryption image of encrypting [ frames only

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2010 International Conference on Information, Networking and Automation (ICINA)

Figure 4. Encryption image of encrypting [ frames and I Blocks of P, B frames

Figure 5. Encryption image of encrypting all the I, P, B frames

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Figure 6. Original video image after decrypting

V. CONCLUSIONS

This paper proposes the solutions and implementation methods of different security level for digital cinema encryption, based on DaVinci hardware platform and Da Vinci digital multimedia software technology, which guarantees the security of digital movie. Using the support of DaVinci high-level Linux, standardized APls and product­oriented underlying drivers, it's significant to reduce the complexity of software design, shorten the development cycles of products, and reduce development costs. The test results show that the design plan we proposes meets the needs of the actual security level, and the digital cinema projection system has a high stability and reliability. Meanwhile, the design methods proposed can be used for other confidential fields. Therefore, the design methods proposed have an extensive reference.

REFERENCES

[I] Zhang Peimin. To Speed up the Development of Digital Cinema of China [A].Video Technology, 2004.9:7-9.

[2] Chen Shaozhen. Cryptography Basics.Bei Jing:Science Press, 2008.05.

[3] Gu Dawu.The advanced encryption standard (AES) algorithm-Rijndael design. Bei Jing:TSINGHUA Universicity Press,2003 .. 03.

[4] DaVinci for Digital Video.http://www.ti.com.2006.

[5] The Future of Digital Video.http://www.ti.com.2006.

[6] Xu Peng, Zhou Haobing.TMS320DM6446 Video Research Based on DaVinci technology [J]. Electronic World,2006(2)135-137.

[7] Tang, L.Methods for Encrypting and Decrypting MPEG Video Data Efficiently[C]. In Proceedings of the Fourth ACM International Multimedia Conference(ACM Multimedia 96). 1996.

[8] B. Bhargava, C.Sh, i and S-Y Wang.MPEG Video Encryption Algorithms[M]. Multimedia Tools and Applications,2004.

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