KR20180064832A - Method for encrypting bitstream, bitstream encryptor using the same, and bitstream encrypting device including the same - Google Patents

Abstract

According to an embodiment of the present invention, a bitstream encrypting method capable of encrypting a texture of an area of interest in an encoded bitstream comprises the following steps: extracting texture data of an area of interest from encoded bitstream; generating encrypted texture data by encrypting the extracted texture data; and generating bitstream in which the area of interest is encrypted based on the remaining data excluding the texture data and the encrypted texture data in the encoded bitstream.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of encrypting a bitstream, a bitstream encryptor using the same, and a bitstream encrypting apparatus using the same. BACKGROUND ART < RTI ID = 0.0 >

The technical idea of the present invention relates to a method of encrypting a bitstream, a bitstream encryptor using the same, and a bitstream encryption apparatus using the same, and more particularly, to a method and apparatus for encrypting a texture of a region of interest A bit stream encrypting method using the same, and a bit stream encrypting apparatus including the same.

Recently, CCTV (closed-circuit television) is widely installed in public facilities, offices, factories, convenience stores, kindergartens, etc. for the purpose of accident, crime prevention and field surveillance.

However, although CCTV achieves the purpose of public safety, it has problems of privacy infringement and exposure of surveillance images.

A method of encrypting a bitstream according to the technical idea of the present invention, a bitstream encryptor using the same, and a bitstream encryption apparatus using the same, is characterized in that a texture of a region of interest is encoded in an encoded bitstream A method for encrypting a bitstream that can be encrypted, a bitstream encryption device using the same, and a bitstream encryption device including the same.

According to an aspect of the present invention, there is provided a method of encrypting a bitstream, the method including extracting texture data of a region of interest from an encoded bitstream, encrypting the extracted texture data, And generating an encrypted bitstream based on the encrypted texture data and the remaining data excluding the texture data in the encoded bitstream.

According to an exemplary embodiment, the step of generating the encrypted texture data entropy-decodes the extracted texture data, the step of entropy-decoding the entropy-decoded texture data, the entropy coding of the encrypted texture data, And generating the texture data.

According to an exemplary embodiment, the step of generating the encrypted bit stream of the ROI comprises generating the encrypted bit stream based on the residual data and the entropy coded texture data .

According to an exemplary embodiment, encrypting the entropy decoded texture data may be encrypted using the RC4 algorithm.

According to an exemplary embodiment, each of the entropy coding and the entropy decoding may use run length coding.

According to an exemplary embodiment, encrypting the entropy decoded texture data may selectively encrypt only non-zero AC coefficient values among the DC coefficient values and AC coefficient values in the entropy decoded texture data.

According to an exemplary embodiment of the present invention, it is determined whether or not the ROI is moved before the ROI is generated, and when the ROI is moved, Reconstructing at least one of uni-directional predicted pictures and bi-directional predicted pictures into an intra-picture. The method may further comprise reconstructing at least one of uni-directional predicted pictures and bi-directional predicted pictures into an intra-picture.

According to an exemplary embodiment, the step of determining whether to move the ROI includes: determining whether the ROI of interest is based on an appearance of a PPS (Picture Parameter Set) Network Abstraction Layer (NPS) within the encoded bitstream; Can be determined.

According to an exemplary embodiment, the period of performing the reconstructing step may be shorter than the appearance period of the intra-encoded image of the encoded bitstream.

According to an exemplary embodiment, the step of extracting the texture data may further include detecting the region of interest from the encoded bitstream.

According to an exemplary embodiment, the step of extracting texture data of the ROI comprises the steps of: extracting motion vectors from among an IDR (Instantaneous Decoding Refresh) NAL and a non-IDR NAL corresponding to the ROI in the encoded bitstream; ) Is excluded, texture data of the region of interest can be extracted.

According to an aspect of the present invention, there is provided a bitstream encoder comprising: a region of interest extractor for extracting texture data of a region of interest from an encoded bitstream; And an adder for generating an encrypted bitstream based on the encrypted texture data and the remaining data excluding the texture data in the encoded bitstream.

According to an exemplary embodiment, an entropy decoding unit entropy decoding the texture data extracted from the ROI extractor, an encryption module encrypting the entropy decoded texture data, and entropy-coded entropy-coded texture data And an entropy coding unit for generating an entropy coding unit.

According to an exemplary embodiment of the present invention, it is determined whether or not the ROI is moved. When the ROI is moved, uni-directional predicted pictures of the encoded bitstream and bidirectional predictive- and reconstructing at least one of bi-directional predicted pictures into an intra picture.

An apparatus for encoding a bitstream according to an aspect of the present invention includes an encoder for encoding a received bitstream and a decoder for extracting texture data of a region of interest from an encoded bitstream, Includes a bitstream encryptor for generating encrypted texture data to generate an encrypted bitstream based on the encrypted texture data and the remaining data excluding the texture data in the encoded bitstream can do.

The method and apparatus according to embodiments of the present invention can effectively utilize the existing encoder structure without modification as the encoded bit stream is encrypted.

In addition, the method and apparatus according to embodiments of the present invention can reconstruct and encrypt an encoded bit stream, thereby reducing the temporal drift error that occurs as the encoded bit stream is encrypted It is effective.

In addition, the method and apparatus according to embodiments of the present invention can improve encryption efficiency by selectively encrypting a region of interest of an encoded bitstream.

BRIEF DESCRIPTION OF THE DRAWINGS A brief description of each drawing is provided to more fully understand the drawings recited in the description of the invention.
1 is a block diagram of an encryption / decryption system according to an embodiment of the present invention.
2 is a block diagram of the encryption apparatus shown in Fig.
3 is a diagram for explaining a temporal drift error that may occur as a result of encrypting an encoded bit stream.
FIG. 4 is a diagram for explaining a bitstream reconstruction process performed in the temporal drift compensator of FIG. 1;
5 is a diagram showing the structure of an encoded bit stream.
FIG. 6 is a diagram illustrating an embodiment in which temporal drift error is mitigated when encryption is performed according to an embodiment of the present invention.
7 is a flowchart of a method of encrypting a bitstream according to an embodiment of the present invention.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. However, it should be understood that the technical idea of the present invention is not limited to the specific embodiments but includes all changes, equivalents, and alternatives included in the technical idea of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0029] In the following description of the present invention, a detailed description of known technologies will be omitted when it is determined that the gist of the present invention may be unnecessarily obscured. In addition, numerals (e.g., first, second, etc.) used in the description of the present invention are merely an identifier for distinguishing one component from another.

Also, in this specification, when an element is referred to as being "connected" or "connected" with another element, the element may be directly connected or directly connected to the other element, It should be understood that, unless an opposite description is present, it may be connected or connected via another element in the middle.

It should be noted that the terms such as " unit, "" to, "and" to module ", as used herein, mean units for processing at least one function or operation, Or a combination of hardware and software.

It is to be clarified that the division of constituent parts in this specification is merely a division by each main function of each constituent part. That is, two or more constituent parts to be described below may be combined into one constituent part, or one constituent part may be divided into two or more functions according to functions that are more subdivided. In addition, each of the constituent units described below may additionally perform some or all of the functions of other constituent units in addition to the main functions of the constituent units themselves, and that some of the main functions, And may be carried out in a dedicated manner.

Hereinafter, embodiments according to the technical idea of the present invention will be described in detail.

1 is a block diagram of an encryption / decryption system according to an embodiment of the present invention.

1, the encryption and decryption system 10 includes a bitstream source 50, a cryptographic apparatus 100, a decryption apparatus 300, and a plurality of bitstream receivers 510 and 520 .

According to an embodiment, the encryption / decryption system 10 may be implemented as a system for encrypting or decrypting image data photographed through a closed-circuit television (CCTV), but is not limited thereto.

The bitstream source 50 may generate a bitstream and provide the generated bitstream to the encryption device 100.

The encryption apparatus 100 may include an encoder 150 and an encryptor 200.

The encoder 150 may receive a bitstream transmitted from the bitstream source 50, and may encode the received bitstream to output an encoded bitstream. The encoder 150 may transmit the encoded bitstream to the encryptor 200.

The encryptor 200 may receive the encoded bitstream transmitted from the encoder 150 and may encrypt only the texture of the region of interest of the received encoded bitstream. The encryptor 200 may transmit the encrypted bitstream of the texture of the region of interest to the decryption apparatus 300. [

According to the embodiment, the encryptor 200 encrypts information necessary for decrypting the decryption apparatus 300 (for example, information on a region of interest, location information of texture data of a region of interest, etc.) To the decryption device 300. [

The detailed structure and operation of the encoder 150 and the encryptor 200 will be described in detail with reference to FIG. 2 to FIG.

According to the embodiment, the encryption apparatus 100 and the decryption apparatus 300 can communicate via wired or wireless communication.

The decoding apparatus 300 may include a decoder 350 and a decryptor 400.

The decoder 350 can decode and output the encrypted bitstream of the texture of the region of interest transmitted from the encryption apparatus 100. [ The decoder 350 may output the decoded bitstream to the decoding apparatus 300 and the first bitstream receiver 510.

The decoding apparatus 300 receives the bit stream decoded and output by the decoder 350, decodes the received bit stream, and outputs the decoded bit stream. The decoding apparatus 300 may output the decoded bit stream to the second bit stream receiver 520. [

The first bitstream receiver 510 can identify the bitstream in a state where the region of interest is encrypted.

The second bitstream receiver 520 can identify the bitstream in a state where the ROI is decoded.

The first bitstream receiver 510 and the second bitstream receiver 520 may be classified according to the access authority. Depending on the embodiment, only those users with access to the region of interest may be set to the second bitstream receiver 520.

2 is a block diagram of the encryption apparatus shown in Fig. 3 is a diagram for explaining a temporal drift error that may occur as a result of encrypting an encoded bit stream. FIG. 4 is a diagram for explaining a bitstream reconstruction process performed in the temporal drift compensator of FIG. 1; 5 is a diagram showing the structure of an encoded bit stream.

Referring to FIGS. 1 and 2, the encryption apparatus 100 may include an encoder 150 and an encryptor 200.

2 illustrates an exemplary structure of the encoder 150, various video codecs such as the H.264 standard and the H.265 standard may be applied to the encoder 150, The structure within the body may be variously modified.

The encoder 150 includes an intra predictor 152, a motion compensator 154, a motion estimator 156, a subtractor 158, a transform unit 160, a quantization unit 162 An entropy coding unit 164, an inverse quantization unit 166, an inverse transform unit 168, an adder 170, a de-blocking filter 172, and a frame memory 174 .

The encoder 150 performs encoding in an intra mode or an inter mode with respect to the bit stream input from the bit stream source 50, and outputs the encoded bit stream.

Intra prediction is performed in the intra mode, and the intra prediction unit 152 can be connected to the switch in accordance with the switching. The intraprediction unit 152 may perform block prediction using pixel data of a block adjacent to a block to be predicted.

 Inter-picture prediction is performed in the inter mode, and the motion compensation unit 154 can be connected to the switch in accordance with the switching. The motion compensation unit 154 may perform block prediction of the current picture using a reference picture stored in the frame memory 174. [

The motion estimation unit 156 searches for a macroblock most similar to the macroblock in the current frame in the previous frame and obtains a motion vector indicating the position difference of the macroblock based on the search result.

The subtractor 158 subtracts the difference between the block data of the current picture and the block data output from the intraprediction unit 152 or the block data of the current picture and the block data output from the motion compensation unit 154, Lt; / RTI > Thereafter, the amount of data may be reduced as the encoding process is performed on the residuals.

The conversion unit 160 may convert the residual output from the subtractor 158. [ According to an embodiment, the transforming unit 160 may output a discrete cosine transform coefficient by performing a discrete cosine transform (DCT) on a sample output from the subtractor 158. [

The quantization unit 162 can quantize the residual, for example, the discrete cosine transform coefficient, which is transformed and output from the transform unit 160. [

The entropy coding unit 164 entropy-codes the quantized data in the quantization unit 162 and outputs the entropy-encoded, i.e., encoded, bitstream to the encryptor 200. [

The inverse quantization unit 166, the inverse transform unit 168, the adder 170, and the de-blocking filter 172 may perform a process of restoring the current picture with the quantized data.

The inverse quantization unit 166 can dequantize the quantized data in the quantization unit 162. [ The inverse transform unit 168 may inversely transform the inverse quantized data output from the inverse quantization unit 166. [ The de-blocking filter 172 performs filtering to reduce block distortion occurring during encoding and outputs the de-quantized signal to the inverse quantization unit 166, the inverse transform unit 168, the adder 170, and the de-blocking filter 172 The current picture restored through the frame memory 174 may be stored in the frame memory 174. [

The encryptor 200 includes a region of interest (ROI) moving detector 202, a temporal drift compensator 204, an ROI data extractor 206, an encryption unit 210 ), And an adder 218. [

Referring to FIG. 3, a case where a ROI is shifted when a reference picture is compared with a current picture is shown.

In this case, no problem occurs when the non-interest area of the current picture refers to the non-interest area of the reference picture (CASE1) and when the interest area of the current picture refers to the interest area of the reference picture (CASE2) When the non-interest area refers to the ROI of the reference picture (CASE3), a temporal drift error occurs in which the ROI moves due to the reference to the ROI, .

Returning to FIG. 2, the encryptor 200 according to an embodiment of the present invention includes a region of interest movement detector 202 and a temporal drift compensator 204 to reduce the temporal drift.

The region of interest motion detector 202 may determine whether the region of interest is moved from the encoded bitstream transmitted from the encoder 150.

According to an embodiment, the region of interest detector 202 may determine whether the region of interest is moving based on the appearance of a Picture Parameter Set (PPS) Nework Abstraction Layer (NAL).

As a result of the determination, if there is movement of the ROI, the ROI detector 202 may transmit the encoded bit stream transmitted from the encoder 150 to the temporal drift compensator 204. [

As a result of the determination, if there is no movement of the ROI, the ROI detector 202 may transmit the encoded bitstream transmitted from the encoder 150 to the ROI extractor 206. [

The temporal drift compensator 204 may reconstruct the encoded bit stream.

Referring to FIG. 2 and FIG. 4 together, the temporal drift is generated by motion estimation and motion compensation, and the dependence by motion estimation and motion compensation is determined until a new intra-picture (I picture) It continues.

In order to mitigate the temporal drift due to the dependency, the temporal drift compensator 204 performs a temporal drift compensator 204 using uni-directional predicted pictures (P pictures) and bi-directional predicted pictures , And a B picture (not shown)) can be reconstructed into an I picture.

When the P picture or the B picture is reconstructed into the I picture when the region of interest appears according to the operation of the temporal drift compensator 204, the appearance period of the I picture becomes shorter than the appearance period of the I picture in the original image, Time drift can be mitigated even when encryption is performed.

The encoder 200 may not include the region of interest detector 202 and the temporal drift compensator 204 where the encoded bit stream is transmitted directly to the region of interest extractor 206 .

2, the region of interest extractor 206 receives the encoded bit stream processed and output from the encoded bit stream or temporal drift compensator 204, and extracts the texture data of the region of interest from the encoded bit stream .

The region of interest is composed of independent slices and encoded. Of the multiple slices included in one picture, the last slice represents the background, and the remaining slices represent the region of interest.

Referring to FIGS. 2 and 5, since the position information of each slice is defined in a PAL (Picture Parameter Set) NAL (Nework Abstraction Layer), position information of slices corresponding to a region of interest (top-left MB address) and bottom-right MB address (bottom-right MB address)) can also be obtained by referring to the PPS NAL.

The ROI extractor 206 extracts a NAL corresponding to the ROI from among the IDR (Instantaneous Decoding Refresh) NAL and the non-IDR NAL following the PPS NAL through the location information of the ROI obtained by referring to the PPS NAL .

The ROI extractor 206 may extract the texture data from the extracted NAL corresponding to the ROI.

According to an embodiment, the region of interest extractor 206 may extract an NAL (e.g., a non-IDR NAL) consisting only of motion vectors from an IDR NAL, a non-IDR NAL corresponding to a region of interest, Only the texture data corresponding to the texture data can be extracted.

Since the encoded bitstream structure shown in FIG. 5 is a known structure, a detailed description thereof will be omitted.

2, the texture data of the ROI extracted by the ROI extractor 206 is transmitted to the encryption unit 210, and the remaining data (for example, non-ROI data) extracted by the ROI extractor 206 The data of the region and the motion vector data of the region of interest) may be transmitted to the adder 218.

The encryption unit 210 may include an entropy decoding unit 212, an encryption module 214, and an entropy coding unit 216.

The entropy decoding unit 212 may perform entropy decoding on the texture data of the ROI extracted by the ROI extractor 206. [

The encryption module 214 can encrypt the entropy-decoded texture data of the region of interest by the entropy decoding unit 212. [

According to an embodiment, the encryption module 214 may include a memory for storing the encryption key.

According to another embodiment, the encryption module 214 may encrypt the texture data of the entropy decoded region of interest using the RC4 algorithm.

According to another embodiment, the encryption module 214 may selectively perform encryption on non-zero AC values among the DC coefficient value and the AC coefficient value in texture data of the entropy decoded region of interest. In this case, since encryption is performed only for a part of data, a reduction in coding efficiency due to encryption can be prevented.

The entropy coding unit 216 can again entropy code the texture data of the region of interest encrypted by the encryption module 214 and output it.

According to the embodiment, the entropy decoding unit 212 and the entropy coding unit 216 may use run length coding.

The adder 218 adds the remaining data (for example, data of the non-interest area and motion vector data of the ROI) extracted by the ROI extractor 206 to the encoded data output from the encoding unit 210 By combining, the region of interest can generate an encrypted bitstream.

FIG. 6 is a diagram illustrating an embodiment in which temporal drift error is mitigated when encryption is performed according to an embodiment of the present invention.

Referring to FIG. 2 and FIG. 6 (a) to FIG. 6 (c), FIG. 6 (a) shows a case where reconstruction of the encoded bit stream by the temporal drift compensator 204 is not performed, Shows a case where an I picture is reconstructed at a 30-frame period, and Fig. 6 (c) shows a case where an I-picture is reconstructed at a 15-frame period.

The temporal drift is further relaxed in FIG. 6 (b) rather than in FIG. 6 (a) and in FIG. 6 (c) rather than in FIG. 6 (b).

1 to 6, the decryption apparatus 300 may be configured to correspond to the structure of the encryption apparatus 100, and may be configured to encode and encrypt the encryption apparatus 100, It is possible to perform decoding and decoding in the reverse order of steps.

7 is a flowchart of a method of encrypting a bitstream according to an embodiment of the present invention.

Referring to FIGS. 1 to 7, the encryptor 200 may receive a bitstream encoded by the encoder 150 (S10).

Depending on the embodiment, the bitstream may be received encoded in various video codecs, such as the H.264 standard, the H.265 standard, and the like.

The ROI detector 202 may detect the ROI in the encoded bitstream (S12).

The ROI detector 202 can determine whether the detected ROI has been moved (S14).

According to an embodiment, the region of interest motion detector 202 may determine whether to move the region of interest based on the appearance of the PPS NAL.

When the ROI detector 202 determines that the ROI has moved, the temporal drift compensator 204 may reconstruct the encoded bitstream (S16).

According to an embodiment, the region of interest motion detector 202 may reconstruct at least one of an I picture and a B picture of the encoded bit stream into an I picture.

The ROI extractor 206 extracts only the texture data of the ROI (S18).

According to an embodiment, if the ROI detector 202 determines that the ROI has not moved, step S16 may be omitted.

The encryption unit 210 may encrypt the texture data of the ROI extracted by the ROI extractor 206 (S20).

According to the embodiment, the encryption unit 210 can encrypt the region of interest texture by sequentially performing entropy decoding, encryption, and entropy coding.

The adder 218 adds the remaining data (for example, data of the non-interest area and motion vector data of the ROI) extracted by the ROI extractor 206 to the encoded data output from the encoding unit 210 By combining, the region of interest can generate an encrypted bitstream (S22).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Various modifications and variations are possible.

10: Encryption decryption system
100: Encryption device
150: Encoder
200: Encryptor
202: region of interest shift detector
204: Time Drift Compensator
206: ROI extractor
210:
300: Decryption device
350: decoder
400: Decoder

Claims (15)

Extracting texture data of a region of interest from an encoded bitstream;
Encrypting the extracted texture data to generate encrypted texture data; And
And generating an encrypted bit stream based on the encrypted texture data and the remaining data excluding the texture data in the encoded bit stream.
The method according to claim 1,
Wherein the generating the encrypted texture data comprises:
Entropy decoding the extracted texture data;
Encrypting entropy-decoded texture data; And
Entropy coding the encrypted texture data to generate entropy coded texture data.
3. The method of claim 2,
Wherein the step of generating the encrypted bitstream comprises:
And generating the encrypted bitstream based on the residual data and the entropy coded texture data.
3. The method of claim 2,
Wherein encrypting the entropy-decoded texture data comprises:
A method for encrypting a bitstream, the method comprising encrypting using an RC4 algorithm.
3. The method of claim 2,
Each of the entropy coding and the entropy decoding is a method of encrypting a bitstream, using run length coding
3. The method of claim 2,
Wherein encrypting the entropy-decoded texture data comprises:
And selectively encrypting only non-zero AC coefficient values among DC coefficient values and AC coefficient values in the entropy decoded texture data.
The method according to claim 1,
Before the step of generating the encrypted bitstream,
Determining whether the region of interest is moved; And
As a result of the determination, when the region of interest is moved, at least one of uni-directional predicted pictures and bi-directional predicted pictures of the encoded bitstream is referred to as an intra- further comprising the step of reconstructing the bitstream into an intra picture.
8. The method of claim 7,
Wherein the step of determining whether to move the ROI comprises:
And determining whether to move the ROI based on the appearance of a PAL (Picture Parameter Set) Network Abstraction Layer (NPS) within the encoded bitstream.
8. The method of claim 7,
The period of performing the reconstructing step may be,
Encoded video is shorter than an appearance period of the intra-encoded video of the encoded bitstream.
The method according to claim 1,
Before the step of extracting the texture data,
And detecting the region of interest from the encoded bitstream.
11. The method of claim 10,
Wherein the extracting of texture data of the ROI comprises:
Extracting texture data of the ROI by excluding an NAL consisting of motion vectors only from an IDR (Instantaneous Decoding Refresh) NAL and a non-IDR NAL corresponding to the ROI in the encoded bitstream, Lt; / RTI >
A region of interest extractor for extracting texture data of a region of interest from an encoded bitstream;
An encryption unit for encrypting the extracted texture data to generate encrypted texture data; And
And an adder that generates an encrypted bitstream based on the encrypted texture data and the remaining data excluding the texture data in the encoded bitstream.
13. The method of claim 12,
An entropy decoding unit for entropy decoding the texture data extracted from the ROI extractor;
An encryption module for encrypting entropy-decoded texture data; And
And an entropy coding unit for entropy coding the encrypted texture data to generate entropy coded texture data.
13. The method of claim 12,
Directional predicted pictures of the encoded bitstream and bi-directional predicted pictures of the encoded bitstream when the ROI is determined as a result of the determination, Further comprising a temporal drift compensator for reconstructing at least one of the at least one of the intra-picture and the at least one intra picture.
An encoder for encoding the received bitstream; And
Extracting texture data of a region of interest from an encoded bitstream, encrypting the extracted texture data to generate encrypted texture data, extracting remaining data excluding the texture data in the encoded bitstream, And a bitstream encryptor for generating an encrypted bitstream based on the encrypted texture data.

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