• Annual Conference of KIPS
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• 2004.05a
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• pp.1213-1216
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• 2004

본 논문에서는 의료계의 PACS의 도입으로 디지털 의료영상 보안을 위한 방법으로, 디지털 워터마킹 기법(Digital Watermarking Technique)중 불법적인 위/변조 검증을 위한 워터마킹 기법을 제안한다. 제안된 워터마킹 방법은 의료영상의 인증과 무결성을 확인 할 수 있는 워터마킹 기법으로, 워터마크 삽입 추출시 블록 이산여현변환(discrete cosine transform)을 사용하여, 저주파 성분을 해쉬함수의 입력으로 하여 해쉬된 값을 시각적으로 인지할 수 있는, 이진영상과 함께 고주파 성분에 워터마크로서 선택적으로 삽입하여, 인증을 통한 국부화(localization)로 영상의 위/변조를 검증하고, 저작권도 확인할 수 있는 의료영상에 적합한 세미 프라질 워터마킹(semi-fragile watermarking)이다.

• Annual Conference of KIPS
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• 2024.05a
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• pp.331-332
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• 2024

최근 디지털 워터마킹 기술은 디지털 콘텐츠의 저작권 보호 및 추적을 위해 활용되고 있다. 그러나 종래의 워터마킹 기술은 이미지에 워터마크 이미지 전체를 삽입하기 때문에 왜곡 공격에 취약하다. 이러한 문제를 해결하기 위해 본 연구에서는 워터마크 분할 삽입 기법을 제안하였다. 워터마크 분할 삽입 기법을 사용하면 종래 방법 대비 20%p의 손실률이 증가하더라도 원본 워터마크를 복구할 수 있어 1.5배 향상된 성능을 보인다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.5
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• pp.9-20
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• 2000

In this paper we compare two frequency domain digital watermarking methods for digital Images, namely DCT(Discrete Cosine Transform) based and DFT(Discrete Fourier Transform) based methods. Unlike DCT coefficients, which always have real values, DFT coefficients normally have complex values Therefore, the DFT coefficients have amplitude and phase components Among them, the phase components are known to carry more Important information for the Images. So, we insert the watermark to the phase of the DFT coefficients only This DFT watermarking method is compared with the conventional DCT based watermarking method for the object-based watermarking problem. Experimental results show that the DFT-phase based method IS more robust to general Image processing attacks including resize, lossy compression(JPEG), blurring and median filtering. On the other hand, the DCT based method is more robust to the malicious attack which inserts different watermarks.

• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.864-871
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• 2006

With the advancement of the digital broadcasting and popularity of Internet, there is an increasing demand for digital data. Recently, several studies have been made on the digital watermarking for copyright protection of digital data. We propose a blind video watermarking using minimum modification of motion vectors. Conventional methods based on motion vectors do watermarking using modification of motion vectors. However, change of motion vectors results in the degradation of video quality. Thus, our proposed algorithm minimizes modification of the original motion vectors to avoid degradation of video quality using simple embedded conditions. Besides, our scheme guarantees the amount of embedded watermark data using the adaptive threshold considering the human visual characteristic. In addition, this is compatible with current video compression standards without changing the bitstream. Experimental result shows that the proposed scheme obtains better video quality than other previous algorithms by about $0.5{\sim}1.0\;dB$.

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.109-117
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• 2010

Digital watermarking has drawn extensive attention for protecting digital contents from unauthorized copying. This paper proposes a new watermarking scheme in frequency domain for copyright protection of digital audio. In our proposed watermarking system, the original audio is segmented into non-overlapping frames. Watermarks are then embedded into the selected prominent peaks in the magnitude spectrum of each frame. Watermarks are extracted by performing the inverse operation of watermark embedding process. Simulation results indicate that the proposed scheme is robust against various kinds of attacks such as noise addition, cropping, resampling, re-quantization, MP3 compression, and low pass filtering. Our proposed watermarking system outperforms Cox's method in terms of imperceptibility, while keeping comparable robustness with the Cox's method. Our proposed system achieves SNR (signal-to-noise ratio) values ranging from 20 dB to 28 dB. This is in contrast to Cox's method which achieves SNR values ranging from only 14 dB to 23 dB.

• Journal of KIISE:Information Networking
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• v.30 no.1
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• pp.17-23
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• 2003

In this Paper. we Propose a digital watermarking scheme for digital images based on a perceptual model, the frequency masking, texture making, and luminance masking Properties of the human visual system(HVS), which have been developed in the context of image compression. We embed two types of watermark, one is pseudo random(PN) sequences, the other is a logo image. To embed the watermarks, original images are decomposed into $8\times8$ blocks, and the discrete cosine transform(DCT) is carried out for each block. Watermarks are casted in the low frequency components of DCT coefficients. The perceptual model adjusts adaptively scaling factors embedding watermarks according to the local image properties. Experimental results show that the proposed scheme presents better results than that of non-perceptual watermarking methods for image qualify without loss of robustness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.878-883
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• 2020

Cryptographic algorithms are used to prevent the illegal manipulation of data. They are divided into public-key cryptosystems and symmetric-key cryptosystems. Public-key cryptosystems require considerable time for encryption and decryption compared to symmetric-key cryptosystem. On the other hand, key management, and delivery are easier for public-key cryptosystems than symmetric-key cryptosystems because different keys are used for encryption and decryption. Furthermore, hash functions are being used very effectively to verify the integrity of the digital content, as they always generate output with a fixed size using the data of various sizes as input. This paper proposes a method using RSA public-key cryptography and a hash function to determine if a digital image is deformed or not and to detect the manipulated location. In the proposed method, the entire image is divided into several blocks, 64×64 in size. The watermark is then allocated to each block to verify the deformation of the data. When deformation occurs, the manipulated pixel will be divided into smaller 4×4 sub-blocks, and each block will have a watermark to detect the location. The safety of the proposed method depends on the security of the cryptographic algorithm and the hash function.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.5
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• pp.378-387
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• 2003

Digital watermarking is the technique that embeds invisible signalsincluding owner identification information, specific code, or pattern into multimedia data such as image, video and audio. Watermarking techniques can be classified into two groups; robust watermarking and fragile(semi-fragile) watermarking. The main purpose of the robust watermarking is the protection of copyright, whereas fragile(semi-fragile) watermarking prevents image or video data from illegal modifications. To achieve this goal watermark should survive from unintentional modifications such as random noise or compression, but it should be fragile for malicious manipulations. In this paper, an invertible semi-fragile watermarkingalgorithm for authentication and detection of manipulated location in MPEG-2 bit-stream is proposed. The proposed algorithm embeds two kinds of watermarks, which are embedded into quantized DCT coefficients. So it can be applied directly to the compressed bit-stream. The first watermark is used for authentication of video data. The second one is used for detection of malicious manipulations. It can distinguish transcodingin bit-stream domain from malicious manipulation and detect the block-wise locations of manipulations in video data. Also, since the proposed algorithm has an invertible property, recovering original video data is possible if the watermarked video is authentic.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.2
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• pp.45-53
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• 2002

A wavelet-based digital watermarking algorithm is proposed that uses the successive subband quantization and human visual system (HVS). After an original image is decomposed into 4-level by the discrete wavelet transform, perceptually significant coefficients (PSC) of each subband excluding the lowest level subband are utilized to embed the watermark. PSC of the baseband ate chosen according to their amplitude and they are slightly modified to embed the watermark by a conventional embedding method. By the successive subband quantization, PSC of the high frequency subband are chosen and slightly modified according to the HVS. We tested the performance of the proposed algorithm compared with the conventional watermarking algorithm by computer simulation. Experimental results show that the proposed watermarking algorithm produces a better invisibility and robustness than the conventional algorithm.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.1
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• pp.43-50
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• 2005

We proposed a method for embedding coded binary data into EZW bitstreams and extracting embedded data from EZW bitstreams using the traditional EZW decoder. EZW coder have two passes. The first pass, the dominant pass have four symbols, P, N, IZ, ZTR. The second pass is sub-ordinary pass which specifies the value of symbol. In the proposed methods, we use ZTR symbol in the dominant pass. We embed watermark into ZTR symbol in the highest frequency band which original image is transferred by wavelet transform. The proposed digital watermarking method shows good properties for robustness in the low bit rate. Accordingly, based on the proposed digital watermarking, video and 3D image watermarking will become a new area for research in the near future.