KR20090067017A - A frame-based selective encryption methoad and apparatus for real time video transmission on voip - Google Patents

Abstract

A frame-based selective encoding method for transmitting video in real-time in VoIP(Voice over Internet Protocol) and a device thereof are provided to minimize service performance and quality decrease while offering a reliable service to a user. A video packet is generated by packetizing encoded video data(104). A frame type of the video data included in the video packet is determined(106). An encoded video packet is generated by encoding the video packet when the video data included in the video packet is an intra-coded frame(108).

Description

Frame-Based Selective Encryption Methoad and Apparatus for Real Time Video Transmission on VoIP

The present invention relates to a method and apparatus for encrypting and decrypting video data transmitted and received in a Voice over Internet Protocol (VoIP) service, and more particularly, to an intra frame (I-Frame) among video data compressed for a VoIP call. ) And a method and apparatus for selectively encrypting and decrypting only).

Voice over Internet Protocol (VoIP) refers to a communication service technology that enables a call by converting voice data into Internet protocol data packets using part or all of an open Internet Protocol (IP) communication network. In this case, the VoIP network may or may not include an existing public switched telephone network (PSTN) telephone network. In the past, VoIP meant a technology for making a voice call through an IP network, but now, a component that provides various multimedia services (video call, video, data, etc.) via a packet network including an IP-based network. Its meaning has been extended to technology for defining components, protocols, and procedures.

VoIP is a technology that is expected to be in great demand in the future because it can provide services with low call charges because it uses the open Internet network, and can conveniently provide various additional services. However, because VoIP service uses open Internet network, security issue is the most important issue. As VoIP services use the same infrastructure as the public Internet network, security issues are the most important issues. This can be thought of as being divided into service provider system and service protection aspect and personal information protection aspect.

First of all, in terms of system and service protection, as the Internet is popularized, there are threats such as malicious hacking, information leakage, worm virus, denial of service (DoS), and so on. Can be.

In addition, in terms of protecting personal information, it is important to ensure privacy without exposing personal information to others. Since VoIP users share the Internet line, it is possible to eavesdrop on personal calls in various ways on a general network line. Do. For example, eavesdropping can be accomplished by software spoofing by hacking network devices on the transmission path or changing settings, such as exposure of general data communications. Other types of attacks are user and terminal forgery, such as replaying collected packets or session hijacking.

Therefore, encryption of multimedia packets transmitted through VoIP is essential. The most important thing in this VoIP encryption technology is that the security of the call must be maintained while the quality of service (QoS) must not be compromised. However, in the existing methods, especially encryption method for real-time data streaming in VoIP, there is a problem of lowering the quality of service by lowering the QoS such as lowering the screen resolution or compressing all frames of the video data. .

Accordingly, an object of the present invention is to provide a method and apparatus for transmitting video data more efficiently than conventional methods while maintaining QoS by selectively encrypting only a specific frame when transmitting video data in a VoIP service.

Another object of the present invention is to provide a method and apparatus for providing a reliable service to a user while using fewer resources in a video call over VoIP, while maintaining a minimum in performance and quality degradation of the service.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention, which are not mentioned above, can be understood by the following description, and more clearly by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to an aspect of the present invention, there is provided a method of encrypting image data transmitted and received through a wired or wireless network, the method comprising: generating an image packet by packetizing encoded image data; Determining a frame type, and generating an encrypted video packet by encrypting the video packet only when the video data included in the video packet is an intra-coded frame as a result of the determination. do.

The present invention also provides a method of decoding image data transmitted and received through a wired or wireless network, the method comprising: receiving an image packet, determining a frame type of the image data included in the image packet, and determining the image packet And decoding the image packet only when the image data included in the frame is an intra coded frame.

In addition, the present invention is a device for encrypting the image data transmitted and received through the wired and wireless network, a frame determination unit for determining the frame type of the image data included in the image packet, and when the image data is an intra-coded frame as a result of the determination Another feature is to include an encryption unit for generating an encrypted video packet by encrypting the video packet only.

In another aspect, the present invention provides a device for decoding image data transmitted and received through a wired or wireless network, the frame determination unit for determining the frame type of the image data included in the image packet, and the determination only if the image data is an intra frame Another aspect of the present invention includes a decoder that decodes an image packet.

According to the configuration of the present invention as described above, by selectively encrypting only a specific frame when transmitting video data in the VoIP service to solve the problem of performance degradation for the existing video encryption to maintain security through encryption while maintaining QoS Image data can be transmitted.

In addition, this provides a more reliable service to users in video calls over VoIP, while minimizing service performance degradation.

The above objects, features, and advantages will be described in detail with reference to the accompanying drawings, whereby those skilled in the art to which the present invention pertains may easily implement the technical idea of the present invention. In describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

In video telephony over VoIP, video compression is used for video transmission. In general, an image compression technique uses an intra frame (I-frame) and an inter frame to increase the efficiency of image compression.

An intra frame is an independent frame having all image data in a frame as in a general picture, and is encoded and decoded independently of other pictures in a video stream.

An inter frame refers to another frame having a transform value called a motion vector, and is divided into a predictive frame (P-frame) and a bidirectional frame (B-frame). The predictive frame is the first coded P-frame or I-frame, i.e., the forward predictive frame that is encoded and decoded for the nearest past reference picture. A bidirectional frame refers to a frame coded with reference to a front frame or a rear frame or both front and back frames.

The inter frame may remove temporal redundancy in each frame data in a manner called predictive coding, and may transform and compress the data. In addition, spatial redundancy of signals remaining between images may be reduced through a method called transform coding.

As such, the intra frame includes all the information of one image in the frame. In the case of the inter frame, only the outline of the image can be grasped to some extent, but the detailed information of the image cannot be grasped. If a third party takes a video data packet during a video call through a VoIP system, and if the intra frame is encrypted, the third party will only be able to obtain the inter frame. As very difficult. In addition, it is impossible to obtain a complete image even if it is played. Therefore, when sending and receiving video data for video call in a system such as VoIP, it is much more efficient to secure call security by selectively encrypting independent intra frames instead of encrypting all frames as in the conventional method. Will be the way.

1 is a flowchart illustrating an image data encryption process according to the present invention.

First, an image to be transmitted to the other party is acquired through a video acquisition device, for example, a camera attached to a webcam or a phone, for a video call (100). When the image is obtained, the obtained image is encoded (102). The encoded image data is packetized for transmission over the wired or wireless network (104).

At this time, the transmitting system determines the frame type of the video data included in the video packet (106). If the frame of the video data included in the video packet is an intra frame, the transmitting system encrypts the video packet (108). If not, the video packet does not undergo an encryption step.

After passing through the determination step 106 and the encryption step 108, the transmitting system transmits the video packet to the receiving system (110).

2 is a flowchart illustrating a video data decoding process according to the present invention.

The receiving system first receives an image packet transmitted from the transmitting system (200). Then, the receiving side system determines the frame type of the image data included in the image packet (202). If the frame of the video data included in the video packet is an intra frame, the transmitting system decrypts the video packet (204). If the frame is not an intra frame, the video packet does not undergo the decoding step.

After the determination step 202 and the decoding step 204, the receiving system acquires image data from the image packet (206). The obtained image data is decoded 208 to be reproduced by the receiving system 210 (210).

As mentioned above, in VoIP, video compression technology is used for video transmission. Currently, various video compression technologies exist, and video compression techniques used in VoIP require low video compression delay time to support QoS, and high data compression rates in order to be able to use them in low-wired and wireless environments.

One embodiment of the present invention uses H.263 image compression technology to satisfy this requirement. H.263 is a video compression standard originally developed for video conferencing and other video services in PSTN networks. Although the latest compression technology, MPEG4 or H.264, supports twice the QoS of the same throughput compared to H.263, H.263 requires less than a few times to tens of times the latency of H.263. Use 263. However, this is not intended to limit the scope of the invention and the invention can be applied to all other image compression techniques except H.263.

In addition, in one embodiment of the present invention, Real-time Transport Protocol (RTP), a Request For Comments (RFC) standard, is used as a data transmission protocol to provide reliable encryption and prevent replay attacks on a network. use.

Now, a method of determining a frame type of video data included in a video packet by using an H.263 video compression technique will be described. 3 is a diagram illustrating a structure of an H.263 RTP packet used for encrypting and decrypting video data according to an embodiment of the present invention.

As shown in FIG. 3, an RTP packet consists of an RTP header, an H.263 payload header, and an H.263 bitstream. The video packet of the encryption and decryption process according to the present invention described with reference to FIGS. 1 and 2 may be formed as shown in FIG. 3. The RTP header provides information on the transmitted RTP packet, the payload header provides information on the bitstream which is the actual video data, and the bitstream part contains the actual video data.

4 is a diagram illustrating the structure of a payload header among the RTP packet structures of H.263. The H.263 payload header has three formats, mode A, mode B, and mode C. FIG. 3 shows a structure of mode A. (The rest of the modes are described in the RFC 2190 document, so the detailed description is omitted.)

According to FIG. 4, various information is contained in the payload header, of which an 'I' flag is a bit indicating a picture coding type. That is, when the I flag is '0', this indicates that the corresponding payload is an intra frame, and when it is '1', it indicates an inter frame. (This is a flag that is commonly used in the format of mode B and mode C.)

Therefore, in an embodiment of the present invention, by referring to the I flag of the payload header, it may be determined whether the frame type of the image data included in the image packet is an intra frame or an inter frame.

5 is a diagram illustrating a configuration of an image transmission system including an image data encryption apparatus and a decryption apparatus according to the present invention. In FIG. 5, the image transmission system 50 is composed of a transmitting system 500 and a receiving system 510. The transmitting system 500 includes an image data encryption apparatus 508 according to the present invention. The receiving system 510 includes a video data decoding apparatus 514 according to the present invention, respectively.

First, the preprocessing unit 502 captures an image to be transmitted. The obtained image data is subjected to an encoding process through the video encoding unit 504, and the encoded image data is an image packet (streaming packet, RTP packet) for media streaming through the RTP packetizing unit 506. Is converted to.

The encryption apparatus 508 includes a frame determination unit 508a and an encryption unit 508b. The frame determiner 508a determines whether the frame type of the image data included in the image packet is an intra coded frame or an inter coded frame. The encryption unit 508b performs encryption on the image packet only when the frame type of the image data included in the image packet is an intra-coded frame as a result of the determination by the frame determination unit 508a.

The video packet that has undergone these steps is transmitted from the transmitting system 500 in the form of a bit stream, and received by the receiving system 510 through the packet receiver 512. The received image packet is subjected to a decoding step through the decoding device 514.

The decoding device 514 includes a frame determiner 514a and a decoder 514b. The frame determiner 514a determines whether the frame type of the image data included in the image packet is an intra coded frame or an inter coded frame. The decoding unit 514b decodes the image packet only when the frame type of the image data included in the image packet is an intra-coded frame as a result of the determination by the frame determination unit 514a.

Next, the video decoding unit 516 decodes the received image data, and the decoded image data is reproduced frame by frame through the rendering unit 518.

Now, it will be described how much improved the encryption and decryption method of the image data according to an embodiment of the present invention compared to the prior art. Table 1 shows the specifications of the system for testing the encryption and decryption method of the image data according to an embodiment of the present invention.

Number of devices CPU Memory Disk Language Compiler OS One 1.5Ghz 640 Mb 40 Gb C # .NET 2.0 Windows

FIG. 6 is a graph measuring processing delay time when all frames are encrypted, and FIG. 7 is a graph measuring processing delay time when frames are encrypted by a selective encryption method according to an embodiment of the present invention.

In each graph, the X axis represents the order of each frame transmitted, and the Y axis represents the total processing time until each frame is encoded, encrypted, transmitted, decrypted, decoded, and output to the screen.

Equation 1 is used to measure the delay time, and Equation 2 is used to measure Tn.

D (latency) = T2-T1

Here, D (latency) is the processing delay time for the frame, T1 is the time immediately after the RTP packet is received, T2 is the time immediately before the decoded RGB image is displayed, and Tn is the overall delay time.

As shown in FIG. 6, in the case of encrypting all existing frames, the total average processing delay time is 72ms. In contrast, as shown in FIG. 7, in the case of the method according to the exemplary embodiment of the present invention, the total average processing delay time is 46 ms.

As a result, it can be seen that the selective encryption method according to an embodiment of the present invention brings about a performance improvement of about 60 to 65% compared to the existing method. In addition, the delay time of 45ms can be regarded as a suitable delay time for transmitting and compressing an image in real time at 15fps.

As described above, according to the method of the present invention, by selectively encrypting only a specific frame when transmitting video data in a VoIP service, video data can be transmitted more efficiently than existing methods while maintaining QoS.

In addition, it is possible to provide reliable services to users using fewer resources in video calls over VoIP, while minimizing service performance and quality degradation.

The method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium includes all types of computer-readable recording media (tangible media such as CD and DVD as well as intangible media such as carrier waves).

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by.

1 is a flow chart showing a video data encryption process according to the present invention.

2 is a flowchart illustrating a video data decoding process according to the present invention.

3 is a diagram illustrating a structure of an H.263 RTP packet used for encrypting and decrypting video data according to an embodiment of the present invention.

4 is a diagram showing the structure of a payload header in an RTP packet structure of H.263;

5 is a diagram illustrating a configuration of an image transmission system including an image data encryption apparatus and a decryption apparatus according to the present invention.

6 is a graph measuring processing delay time when all frames are encrypted.

7 is a graph measuring processing delay time when frames are encrypted by a selective encryption method according to an embodiment of the present invention.

Claims (12)

In a method for encrypting video data transmitted and received through a wired or wireless network, Packetizing the encoded image data to generate an image packet; Determining a frame type of the image data included in the image packet; Generating an encrypted video packet by encrypting the video packet only when the video data included in the video packet is an intra-coded frame. Encrypting video data, characterized in that it comprises a. The method of claim 1, And transmitting the encrypted video packet using a real-time transport protocol (RTP). The method of claim 1, Determining a frame type of the image data The encryption method of the image data, characterized in that performed by referring to the payload header of the image data. In the method of decoding the image data transmitted and received via a wired or wireless network, Receiving an image packet, Determining a frame type of the image data included in the image packet; Decoding the video packet only when the video data included in the video packet is an intra-coded frame. And decoding the image data. The method of claim 4, wherein The receiving of the image packet is a method of encrypting image data, characterized in that performed using a real-time transmission protocol. The method of claim 4, wherein Determining a frame type of the image data The encryption method of the image data, characterized in that performed with reference to the payload header of the image data. An apparatus for encrypting image data transmitted and received through a wired or wireless network, A frame determination unit determining a frame type of the image data included in the image packet; An encryption unit for generating an encrypted image packet by encrypting the image packet only when the image data is an intra-coded frame as a result of the determination; An apparatus for encrypting video data, comprising: a. The method of claim 7, wherein And a communication unit for transmitting and receiving the encrypted video packet using a real-time transmission protocol. The method of claim 7, wherein The frame determination unit And a frame type of the image data with reference to the payload header of the image data. An apparatus for decoding image data transmitted and received through a wired or wireless network, A frame determination unit determining a frame type of the image data included in the image packet; A decoding unit which decodes the image packet only when the image data is an intra frame as a result of the determination; Decoding apparatus of the image data, characterized in that it comprises. The method of claim 10, And a communication unit which transmits and receives the video packet using a real-time transmission protocol. The method of claim 10, The determination unit And a frame type of the image data is determined by referring to a payload header of the image data.

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