KR20020006302A - An insertion and extraction method of lattice-based digital watermarkings - Google Patents

An insertion and extraction method of lattice-based digital watermarkings Download PDF

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KR20020006302A
KR20020006302A KR1020000039885A KR20000039885A KR20020006302A KR 20020006302 A KR20020006302 A KR 20020006302A KR 1020000039885 A KR1020000039885 A KR 1020000039885A KR 20000039885 A KR20000039885 A KR 20000039885A KR 20020006302 A KR20020006302 A KR 20020006302A
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watermark
lattice
lattice point
image
fft
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KR100360821B1 (en
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임종인
이상진
유혜정
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임종인
고세원
스팍스컴 주식회사
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/46—Embedding additional information in the video signal during the compression process
    • H04N19/467—Embedding additional information in the video signal during the compression process characterised by the embedded information being invisible, e.g. watermarking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
    • H04N21/835—Generation of protective data, e.g. certificates
    • H04N21/8358—Generation of protective data, e.g. certificates involving watermark
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/91—Television signal processing therefor
    • H04N5/913—Television signal processing therefor for scrambling ; for copy protection

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Computer Security & Cryptography (AREA)
  • Editing Of Facsimile Originals (AREA)
  • Image Processing (AREA)

Abstract

PURPOSE: A method for extracting and inserting a digital water marking using a lattice is provided, which is strong against collusion attacks, protects and authenticates CONSTITUTION: The original image passes through FFT or DCT to determines a recognizably definite portion, and information about the determined portion is represented by a lattice point. A water mark is inserted into the portion represented by the lattice point. The water mark is selected such that it does not damage the original image. An error vector value is inserted into the lattice point and FFT or DCT is carried out to generate an image into which the water mark has been inserted.

Description

래티스를 이용한 디지털 워터마킹 추출 및 삽입 방법{An insertion and extraction method of lattice-based digital watermarkings}An insertion and extraction method of lattice-based digital watermarkings

본 발명은 디지털 컨텐츠의 저작권 보호를 위한 디지털 워터마크 삽입 및 추출방법에 관한 것으로, 특히, 원본의 이미지를 디지털화하여 FFT(fast fourier transform) 또는 DCT(discrete cosine transform) 변환을 실행한 후 워터마크를 삽입할 부분을 선택하여 원본의 이미지에 손상이 가지 않는 범위내에서 그 원본의 소유자의 정보를 임의의 노이즈로 놓고 그 선택한 장소에 워터마크를 삽입한 다음 다시 역변환을 실행하여 워터마크가 삽입된 디지털 이미지를 얻게 되는 워터마크 추출 및 삽입 방법에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital watermark insertion and extraction method for copyright protection of digital content, and more particularly, to digitize an original image and then perform a fast fourier transform (FFT) or discrete cosine transform (DCT) transformation. Select the part you want to insert, place the original owner's information as random noise, and insert the watermark in the selected place within the range where the original image is not damaged. A method for extracting and inserting a watermark to obtain an image.

일반적으로 디지털 워터마킹 기술은 값싼 국민형 컴퓨터의 보급과 멀티미디어의 발달, 그리고 인터넷 이용자의 증가로 인하여 디지털 데이터의 불법복제 및 불법합성으로 인한 범죄, 디지털 데이터에 대한 소유권 문제를 효율적으로 보호하기 위한 기술적 대응 수단으로 연구개발 되었다.In general, digital watermarking technology is a technology for efficiently protecting digital data, crimes caused by illegal copying and synthesis of digital data due to the spread of cheap national computers, the development of multimedia, and the increase of Internet users. It was researched and developed as a countermeasure.

디지털 워터마크는 크게 주파수 영역 워터마크와 공간 영역 워터마크로 분류한다.Digital watermarks are largely classified into frequency domain watermarks and spatial domain watermarks.

주파수 영역 워터마크는 영상 데이터를 DCT나 FFT 에 의해 주파수 영역으로 변환하여 그 주파수 영역들 중에서 인간시각으로 덜 민감한 성분에 삽입한다.The frequency domain watermark converts the image data into the frequency domain by DCT or FFT and inserts it into a component less sensitive to human vision among the frequency domains.

이러한 주파수영역 워터마킹 방법은 인간의 시각 시스템을 효과적으로 활용한 것으로 인간 시각으로 감지할 수 없는 영역인 고 주파수 성분에 워터마크를 삽입한다.The frequency domain watermarking method effectively utilizes the human visual system and inserts a watermark into high frequency components, which are areas that cannot be detected by human vision.

공간 영역 워터마크는 인간 시각 시스템을 이용한 방법으로 영상의 밝기 값에 민감하지 않다는 것을 이용하여 영상의 픽셀 값에서 LSB(Least Significant Bit)를 조작하여 윤곽선의 밝기 값을 변화시키는 방법을 이용한다.The spatial domain watermark is a method using a human visual system that is insensitive to the brightness value of an image, and uses a method of changing the brightness value of an outline by manipulating a LSB (Least Significant Bit) in the pixel value of the image.

이러한 공간 영역 워터마킹은 원본영상에 시각적으로 인식할 수 없는 워터마크를 삽입하는데 효과적이지만 일반적인 영상 변화에는 강인하지 못하다는 단점을 지니고 있다.Such spatial domain watermarking is effective to insert a watermark that cannot be visually recognized in the original image, but has a disadvantage in that it is not robust to general image changes.

최근까지 발표된 워터마킹 기술을 살펴보면, 나름대로의 장점과 함께 어느 부분에서는 매우 취약한 단점을 가지고 있다. 예를 들어, Rhoads가 95년도에 발표한 워터마킹 기법은 저역통과(low pass)필터링에 강하다는 장점을 가지고 있지만 공모공격(collusion attacks)에는 매우 취약하다는 단점을 가지고 있다.Looking at the watermarking technology released until recently, it has its own advantages and some weak points. For example, Rhoads' watermarking technique, published in 1995, has the advantage of being strong against low pass filtering, but it is very vulnerable to collusion attacks.

현존하는 대부분의 워터마킹 기법은 안전성에 대한 확실한 이론적 기반이 없을 뿐 아니라 공모 공격에 매우 취약하다할 수 있다.Most existing watermarking techniques lack a solid theoretical basis for safety and can be very vulnerable to collusion attacks.

그리고 모든 값들이 실험치에 의존하므로 워터마킹 기술의 효율성과 안전성 기준이 객관적이지 못하다는 단점이 있다.And since all the values depend on the experimental values, the efficiency and safety criteria of watermarking technology are not objective.

본 발명의 목적은 기존의 워터마킹 방법에 비하여 공모공격에 대해 강인하고 또한 누구나 쉽게 워터마킹을 삽입하고 추출할 수 있으면서 수학적으로 어려운 문제인 래티스 NP-hard 문제에 그 안전성의 기반을 두고 있는 디지털 컨텐츠의 저작권 보호 및 인증을 위한 디지털 워터마킹 삽입 및 추출방법을 제공하는 데 있다.The object of the present invention is to be more robust against collusion attack than the existing watermarking method, and the safety of digital contents based on the safety of the Lattice NP-hard problem, which is a difficult mathematical problem, can be easily inserted and extracted by anyone. The present invention provides a digital watermarking insertion and extraction method for copyright protection and authentication.

상기 목적을 달성하기 위한 본 발명은 원본의 이미지를 FFT 또는 DCT변형을 거쳐 인지적으로 확실한 부분을 결정하고 그 결정된 부분의 회도정보를 래티스 점으로 표현하는 단계와, 상기 래티스 점으로 표현된 부분에 에러회도 벡터 값으로 워터마크를 삽입하는 단계와, 상기 단계 실행 후 역 FFT나 역 DCT를 실행하여 워터마크가 삽입된 이미지를 생성하는 단계를 포함한다.The present invention for achieving the above object is to determine the cognitively certain portion of the original image through the FFT or DCT transformation, and to express the ash information of the determined portion as a lattice point, the portion represented by the lattice point And inserting a watermark with an error degree vector value, and executing an inverse FFT or an inverse DCT after generating the watermark.

이하, 본 발명을 상세하게 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

본 발명은 래티스의 NP-hard 문제를 이용하였다. 래티스는 최단벡터문제(Shortest Vector Problem), 근접벡터문제(Closest Vector Problem), 그리고 최단기저문제(Shortest Basis Problem)의 세 가지 어려운 문제들이 존재한다. 이 중에서 근접벡터문제(CVP)는 NP-hard라는 것이 알려졌다. 이를 본 발명의 워터마킹 기술의 안전성 기반으로 삼고 있다.The present invention takes advantage of the NP-hard problem of lattice. Lattice has three difficult problems: the Shortest Vector Problem, the Closest Vector Problem, and the Shortest Basis Problem. Of these, the proximity vector problem (CVP) is known to be NP-hard. This is based on the safety of the watermarking technology of the present invention.

근접벡터문제는 래티스 점에 어떠한 에러벡터를 더하였을 때, 에러벡터가 더해진 점에서 원래의 래티스 점을 찾아간다는 것은 그 에러벡터를 아는 사람을 제외하고는 불가능하다. 이것은 원래의 래티스 점을 찾는 다항식 시간 알고리즘이 존재하지 않음을 의미한다.Proximity vector problem is that when an error vector is added to a lattice point, it is impossible to find the original lattice point at the point where the error vector is added, except for those who know the error vector. This means that there is no polynomial time algorithm for finding the original lattice point.

이러한 래티스의 어려운 문제를 기초로 한 다양한 래티스 기반 공개키 알고리즘을 구현하고자 한다.We will implement various Lattice-based public key algorithms based on the difficult problems of Lattice.

본 발명에서는 워터마킹을 위해, 원본의 워터마크를 심을 자리의 회도 정보를 래티스 점으로 표현하고 워터마크 값을 에러벡터로 하여 그 래티스 점에 에러벡터를 더 한다. 이후 역 변환을 거쳐 워터마크가 삽입된 이미지를 얻게되는 과정을 거친다.In the present invention, for watermarking, the frequency information of the place where the original watermark is to be planted is expressed as a lattice point and an error vector is added to the lattice point using the watermark value as an error vector. After the reverse conversion, a watermarked image is obtained.

이 과정에 대해 좀더 자세히 살펴보면, 우선 원래의 이미지를 FFT나 DCT변형을 거쳐 인지적으로 확실한 부분을 결정하여 결정된 부분의 회도정보를 래티스 점으로 표현한다.Looking at this process in more detail, first, the cognitive certainty of the original image is determined through FFT or DCT transformation, and the gray information of the determined portion is expressed as a lattice point.

래티스 점으로 표현된 부분에 워터마크를 삽입한다. 이때, 워터마크는 원본의 이미지가 손상이 가지 않는 범위에서 선택되며, 워터마크 값은 에러 회도 값으로 정해진다.Insert a watermark at the part indicated by the lattice point. At this time, the watermark is selected in a range where the original image is not damaged, and the watermark value is determined as an error frequency value.

위의 래티스 점에 에러 회도 벡터 값을 삽입 후 역 FFT나 역 DCT를 거친다음, 원본에 훼손가지 않도록 가식적인 부분을 수정하여 최종적으로 워터마크가 삽입된 이미지를 얻는다.After inserting the error frequency vector value into the lattice point above, it goes through the inverse FFT or the inverse DCT, and then corrects the imaginary part so as not to damage the original, and finally obtains the watermarked image.

여기에서 워터마크가 삽입된 이미지에서 에러벡터 즉, 워터마크를 찾는다거나 원래의 회도 정보를 찾는다는 것은 래티스의 NP-hard 문제이므로 불가능하며 원본 없이도 이미지의 소유를 증명/추출 가능하다.In this case, it is impossible to find the error vector, that is, the watermark or the original circuit information in the watermarked image, because it is a NP-hard problem of Lattice and it is possible to prove / extract the ownership of the image without the original.

다음은 디지털 영상 데이터에 워터마크를 삽입하는 예를 설명한다.The following describes an example of embedding a watermark in digital image data.

먼저 원본에 대해 DCT 또는 FFT 변형을 실행하여 인지적으로 확실한 부분을워터마킹 영역으로 선택한다.First, a DCT or FFT transformation is performed on the original to select the cognitively certain part as the watermarking area.

워터마크를 심을 자리가 확실하게 정해지면, 그곳의 회도 정보를 벡터로 표시한다. 즉, 워터마크 심을 위치가S=(s 1,s 2,···,s n)이라면, 각각의 원소에 대한 회도 값을 계산하고 래티스를 결정한다.Once the place to plant the watermark is clearly determined, the pedestrian information there is displayed as a vector. In other words, if the position of the watermark seam is S = ( s 1 , s 2 , ..., s n ), the degree of circulation is calculated for each element and the lattice is determined.

각각의 회도 값을G=(g s 1,g s 2,···,g s n),g s i∈Z라고 하면, 여기에 원래의 이미지에 훼손을 주지 않을 정도의 에러벡터 E=(e 1,e 2,···,e n)를 결정하여G+E=(g s 1+e 1 ,g s 2+e 2 ,··· ,g s n+e n)을 계산한다.If the values of each degree are G = ( g s 1 , g s 2 , ···, g s n ), g s i ∈ Z , the error vector E = enough to not damage the original image. to determine (e 1, e 2, ··· , e n) and calculates the g + e = (g s 1 + e 1, g s 2 + e 2, ···, g s n + e n) .

여기서G는 래티스 점이면서G+E는 래티스 점이 되지 않도록 하는 에러벡터와 래티스를 선택하였으므로G+E에서E를 찾거나G를 찾는다는 것은 래티스의 NP-hard 문제인 근접벡터 문제이므로 불가능하다. 따라서 워터마크가 안전하게 삽입이 된다.Since G is a lattice point and G + E is an error vector and a lattice that prevents it from becoming a lattice point, finding E or finding G in G + E is not possible because it is a proximity vector problem, which is a NP-hard problem of Lattice. Therefore, the watermark is safely inserted.

이상에서 설명한 바와 같은 본 발명은 디지털 영상 컨텐츠의 저작권 보호 및 인증을 위한 디지털 워터마크의 추출/삽입에 있어 수학적으로 NP-hard 문제인 래티스의 근접벡터문데(CVP)에 안전성기반을 가지고 있다는 점과 워터마킹의 삽입/추출이 용이하고 원본 없이도 워터마크의 추출이 가능하게 되는 특유의 효과가 나타나게 된다.As described above, the present invention has a safety basis in Lattice's proximity vector question (CVP), which is a mathematical NP-hard problem in extracting / inserting digital watermarks for copyright protection and authentication of digital image contents. The unique effect of inserting / extracting marking and extracting the watermark without the original is shown.

Claims (2)

원본의 이미지를 FFT 또는 DCT변형을 거쳐 인지적으로 확실한 부분을 결정하고 그 결정된 부분의 회도정보를 래티스 점으로 표현하는 단계; 상기 래티스 점으로 표현된 부분에 에러회도 벡터 값으로 워터마크를 삽입하는 단계; 상기 단계 실행 후 역 FFT나 역 DCT를 실행하여 워터마크가 삽입된 이미지를 생성하는 단계;를 포함하는 것을 특징으로 하는 래티스를 이용한 디지털 워터마킹 추출 및 삽입방법.Determining an cognitively certain portion of the original image through an FFT or DCT transformation, and expressing the circuit information of the determined portion as a lattice point; Inserting a watermark as an error degree vector value in a portion represented by the lattice point; And executing an inverse FFT or an inverse DCT after the execution of the step to generate an image with a watermark embedded therein. 제 1항에 있어서, 래티스 점으로 표현된 부분에 워터마크를 삽입할 때, 그 워터마크는 원본에 이미지 손상이 가해지지 않는 범위의 값으로 선택되는 것을 특징으로 하는 래티스를 이용한 디지털 워터마킹 추출 및 삽입방법.The digital watermarking extraction method according to claim 1, wherein, when the watermark is inserted into the portion represented by the lattice point, the watermark is selected as a value within a range where no image damage is applied to the original. Insertion method.
KR1020000039885A 2000-07-12 2000-07-12 An insertion and extraction method of lattice-based digital watermarkings KR100360821B1 (en)

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