The Design of Video-Conference

8/6/2019 The Design of Video-Conference

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The Design of Video-Conference

Encryption System based on H.264Hua-Zhen YAO

#1

Zhongkai University of Agriculture andEngineering, Information College

Guangzhou 510225 , China

[email protected]

Ya-Tao JING#2

South China University of TechnologyGuangzhou 510640 , China

[email protected]

Abstract This paper discusses problems about video security

based on H.264 video compression encoding standard, puts

forward a design scheme of encryption about video meeting. The

video encryption system combines with AES (Advanced

Encryption Standard) algorithm, H.264 and the chaos encryption.

In this scheme, AES is used in encrypting DCT Coefficients and

motion vector symbol sequence of H.264. The protection of video

movement information and video texture information is achieved

in this video encryption system. Chaos encryption technology is

used to generate the video conference keys to ensure the

unpredictability of the key. Experiments show that the system

can achieve rapid video encryption computing and smooth video

conferencing .It also can protect video data against wiretapping

and attack ,it improve the confidentiality of the communication,

Group members can be safe and effective authentication services

can be achieved.

Keywords- H.264; video encryption; video conference; AES; chaos

cipherI. INTUODUCTION

With the development of communications networks, the

various departments of enterprise exchanges information

more closely through networks, people are no longer satisfied

by telephone, fax and e-mail, and other traditional voice and

text communications, but they need a new means of

communication that combines data, images, audio and video.Video conference is a new means of communication. At

present, as the main users of video conferencing, such as

government agencies, national defense agencies, and

industrial and mining enterprises etc, the contents of video

conference are often related to state secrets, military

intelligence, business secrets and private information. Video

content must be encrypted before transmission in the network.

In order to meet the needs of real-time transmission and

access of video data the encryption and decryption algorithms

can not bring much delay to the transmission and access.

H.264 is the latest video compression standard [2, its

compression efficiency is also the highest and twice as much

as H.263 and MEPG4 in the similar image quality. H.264 can

greatly enhance compression efficiency and improve

transmission of image data in the network. This paper

discusses problems about video security based on H.264 video

compression encoding standard, puts forward a design scheme

of encryption about video meeting. The video encryption

system combines with AES algorithm, H.264 and the chaos

encryption. In this scheme, AES is used to encrypt video data.

Chaos encryption technology is used to generate the video

conference keys to ensure the unpredictability of the key.

Public key encryption is used in key distribution. Experiments

show that the system can achieve rapid video encryption

computing and smooth video conferencing .It also can protect

video data well and meet the requirements of real-time video.

II. SYSTEM FUNCTION AND FRAMEWORK

In this paper, the video conference system is composed of

participant terminals and Conference Management server as

shown in Figure 1. Conference Management server has a

multicast group for each meeting so that it can maintain anumber of meetings at the same time. Participant terminal is a

direct interactive tools of conference scene, it can complete

synchronization capture, compression, encryption of the local

audio and video and sent out after labeled as standard [8] RTP

packets. At the same time, it can receive RTP data flow and

form them into data frame, and then decrypt, decode, and play

back. The group management server is a Concurrent Server

and based on TCP / IP protocol [5].

978-1-4244-7874-3/10/$26.00 2010 IEEE


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video data flow

control information

conference management server

participant terminal

participantterminal

Multicast

Group 1

Multicast

Group 2

Multicast

Group 3

video code and encryption

apply to join the conference

video decode and decryption

participantterminal

Figure1. Systemic framework

There are two kinds of data stream in this system: the

control information and the video data. The control

information between Participant terminal and conference

management server constitutes control information stream.RTP pack between various parts constitutes video data stream.

Encryption computing is used in control information and

video data. Encryption algorithm is the core of encryption

computing. Encryption algorithm is divided into Symmetric

encryption algorithm (private key) and asymmetric encryption

algorithm (PKI) [3]. Symmetric encryption algorithm has

merits of high encryption speed and high encryption strength.

But it has difficulties in key distribution and management.

Symmetric encryption algorithm can meet the efficiency

needs of video system. Asymmetric encryption algorithm has

low speed but simple key management just can be used in key

distribution of conference management server. The video

encryption conference system in this paper combines the two

kinds of encryption algorithm, it can make the key

management simpler and effectively improve the efficiency of

encryption. Specific interactive process is as follows:

At first participant terminals apply to the join the

videoconference .Management server must authenticate the

identity of participant terminals. Legitimate participants will

be accepted as members of multicast Group. The first one that

apply to join the video conference become Chairman of the

video Conference, the Chairman have the highest control

function .The other participants can be expelled from the

conference by chairman. When the chairman left the video

conference, the conference is suspended.

After participant terminals finish identity

authentication, conference management server randomly

generates a CKey (conference key).Respectively, CKey, the

multicast address and Port information [3] is be encrypted by

the PuKey (pubic key)of each participant terminal ,then

distribute to the participant terminals.

The information that each participant terminal received is be decrypted by the PrKey (private key) of each

participant terminal , then CKey, the multicast address of the

conference and port information will be gained.

The participant terminal who want to send message

generate SKey (video secret key) . SKey is generated by

chaotic mapping algorithm. CKey is as Initial conditions of

chaotic mapping. Skey is used to encrypt video data. The

video data stream of H.264 is encrypted selectively and

multicasted to other members

(5) When other participant terminals receive video data,they also generate SKey by chaotic mapping algorithm .

CKey is also as Initial conditions of chaotic mapping. Video

data will be decrypted by SKey, then be decompressed and

played.

III. IMPROVED VIDEO ENCRYPTION

ALGORITHM

Because the object of encryption is H.264 video

streaming, so a suitable encryption method can be chosen on

the features of H.264 basis. There are two kinds of common

encryption method [6]. The first one is direct encryption

method, video data is be encrypted as ordinary data in this

method, this approach has the highest safety while it has low

speed of encryption relatively. This method make video lose

compatibility since the format information and control

information of video data are also encrypted. The second

method is selective encryption. Generally the actual video

data is encrypted while format information and control

information are not encrypted in this algorithms, it can

maintain the compatibility of encrypted data stream. The

format of data and encryption algorithm are considered

together. Different sensitive data is encrypted to meet

different security needs. Generally this encryption method has

high speed and can meet the real-time requirements of video.

According to the category of encrypted data, this method can

be divided into different categories as following discussion: (1)

Different data frame and data block are encrypted. For


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example, the header and I frame of H.264 are only encrypted,

the other frame is not encrypted. This method has not high

security because of the correlation between different frames.

(2) DCT coefficients are scrambled. 4 4 DCT Integer

Transform is used in H.264, and the purpose of encryption

can be achieved through scrambling of DCT coefficients.While this method is contrary to the energy sequence of

Zig-Zag scan, and it makes the compression ratio of entropy

coding reduce. (3) The symbols DCT coefficient and the

symbols of motion vectors are only encrypted; this method

can reduce complexity greatly and meet the real-time

requirements of video stream. Moreover, if the traditional

encryption algorithm is used, such as DES, high security can

be guaranteed, compatibility and operability of video data also

can be maintained. (4) Format information of video data is

encrypted.Since the real-time requirement of video conference is

high, the idea of selective encryption is adopted in this paper.

Improved VEA (Video Encryption Algorithm) [4] is combined

with AES and an improved integration algorithm is formed.

Since DCT coefficient has large amount of information

and plays an important role in video code, symbols of DCT

coefficient are encrypted by secret key in VEA. The secret

key is a binary random sequence m bits in length and is

defined as K=k1k2kikm. Symbol sequence of DC and AC

coefficients is also a binary sequence and is expressed as

S=s1s2sm sm+1s2m. 0 positive represents sign 1 represents

negative sign in S sequence.

This encryption algorithm can be expressed

as ( ) ( )( ) ( )( ) ( )mmmmmmK skskskskskSE 22112211 = ++ "" , and

represent binary XOR. The encrypted symbol is given back to

the original corresponding data. One part of the symbols is the

same as the original. The other part is changed. The results

of VEA encryption algorithm are reflected in IDCT transform

of video decode. Since the symbols of some DCT

coefficient are changed, the pixel values of image change a lot

after IDCT transform.

Since this encrypted system is based on H.264 video

coding standard. Motion code (motion Prediction and

Compensation) and DCT transform coding occurs In the

process of coding.

Motion Estimation

CKey

Motion vectorMotion Compensation

DCT Ttransform/

Scan / Quantization

Entropy

Coding

Symbol sequence of DCT

coefficients is encrypted

through AES

Video

Sequence

Scan and Inverse

Transform

Filtering

encryption

through

AES

Chaotic mapping SKey

Figure 2.Flow chart of improved video encryption system

Figure 3.contrast before encryption and after decryption

The image texture depends on DCT transform, the

information of movement depends on motion vector. If DCT

coefficient and the motion vector are encrypted, the image

texture and the information of movement will be protected,

safe video transmission is realized. The adopted scheme in

this paper combines the process of encryption and decryption

with the process of code and decode. In this scheme, for

intra-coded block, symbol sequence of DCT coefficients is

encrypted. For motion prediction-coded block and

compensation-coded block, symbol sequence of motion vector

is encrypted. The format information is maintained in the

process of encryption. In the traditional VEA algorithm, the

core operation is XOR; its safety is not very high. In order to

strengthen the security of Video-Conference System, AES

(Advanced Encryption Standard) is adopted to encrypt the

symbol sequence of DCT coefficients and motion vector, The

key of AES can be set to the arbitrary multiplier of 32-bit, the

minimum is 128-bit and the maximum is 256-bit. The key can

not be cracked by exhaustive law. In order to increase the

security of the video encryption system, the secure key of this

system is 128-bit in length and generated by chaos encryption,

the symbol sequence of DCT coefficients and motion vector is

encrypted by AES, encryption process is shown in Figure 2.


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The effect of encryption can be seen in Figure 3, test

image is encrypted and it is difficult to confirm. The

experimental result shows this system can achieve a good

encryption effect. Test results showed that system have good

stability and video plays smoothly, processing time of one

frame is about 6.4 ms, transmission time of 2 KB is about 0.3~ 0.4 ms.

IV. KEY GENERATIONS

Randomicity plays an important role in the calculation

theory and cryptology. The key in this paper is chaotic

sequence based on logistic mapping. Chaotic systems has the

character of pseudo-randomness and is extremely sensitive to

initial conditions, it is also a nonlinear series, has a

complicated structure and is difficult to forecast.

A dynamical system that is researched widely is Logistic

mapping, defined as )1(),(1 nnnn xxxfx ==+ ]4,0(

)1,0(nx .Among all the parameters, is known as

Mycobacterium parameters. Logistic mapping work in the

chaotic state if 45699456.3 < . Chaotic sequence of this

video encryption system is generated by Logistic mapping

when 4= . The input and output of Logistic model

are in range (0, 1) when this logistic model is in a chaotic

state. There are many methods that can be used in the

generation of chaotic sequence; one of the methods is adopted

in this paper. This method can be expressed as following.

(1)The appropriate initial value0x and the time of iterations

n are adopted. (2)Real chaotic sequence )(nX can be

gained after iterative computation. (3) )(nX is quantified

andZis the quantitative threshold, )(nC is quantitative result.

Quantitative process is defined as 0 ( )( )

1 ( )

X i ZC i

X i Z

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The Design of Video-Conference