• The KIPS Transactions:PartB
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• v.12B no.4 s.100
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• pp.421-428
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• 2005

A new method of Semi-fragile image watermarking which ensures the integrity of the contents of digital image is presented. Proposed watermarking scheme embeds watermark in the form of quantization noise on the wavelet transform coefficients in a specific mid frequency subbands selected from a wavelet packet decomposition based on energy distribution of wavelet transform coefficients. By controlling the strength of embedded watermark using HVS (Human Visual System) characteristic, it is imperceptible by a human viewer while robust against non-malicious attack such as compression for storage and/or transmission. When an attack is applied on the original image, it is highly probable that wavelet transform coefficients not only at the exact attack positions but also the neighboring ones are modified. Therefore, proposed authentication method utilizes whether both current coefficient and its neighbors are damaged. together. So it can efficiently detect and accurately localize attacks inflicted on the content of original image. Decision threshold for authentication can be user controlled for different application areas as needed.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2411-2414
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• 2003

In this paper, we present a digital image authentication using semi-fragile watermarking techniques. The algorithm is robust to innocuous manipulations while detecting malicious manipulations. Specifically, the proposed method is designed for the purpose of the real time authentication of an image frame captured from a digital camera due to its easy H/W implementation, security and visible verification. To achieve the semi-fragile characteristics that survive a certain amount of compression, we employ the invariant property of DCT coefficients' quantization proposed by Lin and Chang [1]. The binary watermark bits are generated by exclusive ORing the binary logo with pseudo random binary sequences. Then watermark bits are embedded into the LSBs of pre-quantized DCT coefficients in the medium frequency range. Verification is carried out easily due to visually recognizable pattern of the logo extracted by exclusive ORing the LSBs of the embedded DCT coefficient with pseudo random number seeded by a secret key. By the experiment results, this method is not only robust to JPEG compression but also it detects powerfully alterations of the original image, such as the tempering of images.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.875-878
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• 2001

본 논문에서는 디지털 영상의 변조를 확인함과 동시에 변조의 위치를 확인하는 연성 워터마킹(fragile watermarking)을 위하여 DCT를 통해 블록의 에너지를 계산한 후, 에너지의 단계별로 워터마크의 삽입량을 조절하는 방법을 제안한다. 디지털 영상의 소유권 확인을 위해 디지털 서명을 사용하며, 영상에 DCT를 수행함으로서 모든 픽셀에 워터마크를 삽입하지 않고서도 변조의 유무를 확인하는 것이 가능하 방식이다. DCT 계수로 각 블록의 에너지를 계산하여 블록의 관계를 분류하며 에너지가 작은 블록들과 큰 블록들은 이간의 시각에 민감한 부분이므로 워터마크의 삽입 양을 줄이고, 중간 단계의 블록일수록 워터마크의 삽입 양을 늘린다. 에너지의 단계 분류에 의해 가변적으로 워터마크를 삽입함으로 워터마크의 비가시성과 연성을 만족시키며 변조의 유무와 위치를 확인할 수 있게 된다.

• The Journal of Information Technology
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• v.9 no.4
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• pp.49-55
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• 2006

In this paper, a new fragile watermarking algorithm for digital image is presented, which makes resolving the security and forgery problem of the digital image to be possible. The most suitable watermarking method that verifies the authentication and integrity of the digital image is the Wong's method, which invokes the hash function (MD5). The algorithm is safe because this method uses the hash function of the cryptology. The operations such as modulus, complement, shift, bitwise exclusive-or, bitwise inclusive-or are necessary for calculating the value of hash function. But, in this paper, an Arithmetic encoding method that only includes the multiplication operation is adopted. This technique prints out accumulative probability interval, which is obtained by multiplying the input symbol probability interval. In this paper, the initial probability interval is determined according to the value of the key, and the input sequence of the symbols is adjusted according to the key value so that the accumulative probability interval will depend on the key value. The integrity of the algorithm has been verified by experiment. The PSNR is above the 51.13db and the verifying time is $1/3{\sim}1/4$ of the verifying time of using the hash function (MD5), so, it can be used in the real-time system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4516-4521
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• 2014

Digital watermarking for digital image authentication and integrity schemes are based on fragile watermarking and can detect any modifications in a watermark embedded image by comparing the embedded watermark with the regenerated watermark. Therefore, the digital watermark for image authentication and integrity should be erased easily when the image is changed by digital image processing, such as scaling or filtering etc. This paper proposes an effective tamper detection scheme for digital images. In the proposed scheme, the original image was divided into many non-overlapping $2{\times}2$ blocks. The digital watermark was divided into two LSB of each block and the image distortion was imperceptible to the human eye. The watermark extraction process can be used to determine if the watermarked image has been tampered. The experimental results successfully revealed the effectiveness of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4568-4587
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• 2014

Authentication of videos and images based on the content is becoming an important problem in information security. Unfortunately, previous studies lack the consideration of Kerckhoffs's principle in order to achieve this (i.e., a cryptosystem should be secure even if everything about the system, except the key, is public knowledge). In this paper, a solution to the problem of finding a relationship between a frame's index and its content is proposed based on the creative utilization of a robust manifold feature. The proposed solution is based on a novel semi-fragile watermarking scheme for H.264/AVC video content authentication. At first, the input I-frame is partitioned for feature extraction and watermark embedding. This is followed by the temporal feature extraction using the Isometric Mapping algorithm. The frame index is included in the feature to produce the temporal watermark. In order to improve security, the spatial watermark will be encrypted together with the temporal watermark. Finally, the resultant watermark is embedded into the Discrete Cosine Transform coefficients in the diagonal positions. At the receiver side, after watermark extraction and decryption, temporal tampering is detected through a mismatch between the frame index extracted from the temporal watermark and the observed frame index. Next, the feature is regenerate through temporal feature regeneration, and compared with the extracted feature. It is judged through the comparison whether the extracted temporal watermark is similar to that of the original watermarked video. Additionally, for spatial authentication, the tampered areas are located via the comparison between extracted and regenerated spatial features. Experimental results show that the proposed method is sensitive to intentional malicious attacks and modifications, whereas it is robust to legitimate manipulations, such as certain level of lossy compression, channel noise, Gaussian filtering and brightness adjustment. Through a comparison between the extracted frame index and the current frame index, the temporal tempering is identified. With the proposed scheme, a solution to the Kerckhoffs's principle problem is specified.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.06a
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• pp.506-509
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• 2001

본 논문에서는 디지털 영상의 변조를 확인함과 동시에 변조의 위치를 확인하는 DCT 기반의 fragile watermarking을 제안한다. 디지털 영상의 인증과 무결성을 위해 기존의 Wong이 사용한 해쉬 함수와 비대칭키 암호 알고리즘을 사용하며, 영상에 DCT 변환을 함으로서 영상의 모든 픽셀에 워터마크를 삽입하지 않고서도 변조의 유무를 확인하는 것이 가능하다. 본 논문에서는 DCT 계수 중 일부 저주파 계수의 하위 비트에 워터마크를 삽입하여 워터마크의 비가시성과 연성을 만족하며 변조의 유무와 위치를 확인한 수 있게 된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.2073-2076
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• 2003

본 논문에서는 이산코사인변환의 선형성을 이용하여 정지화상의 위변조를 방지하기 위한 semi-fragile 워터마킹 방법을 제안하였다. 제안한 방법에서는 이산코사인변환의 선형특성을 이용하여 공간영역에서 임의의 DCT 계수를 변형시킬 수 있으므로 이산코사인변환을 행하지 않고도 워터마킹 정보를 삽입할 수 있으므로 빠른 워터마킹 삽입이 가능하다 또한 정해진 DCT 계수에만 워터마킹 정보를 삽입할 수 있으므로 비가시성의 향상을 가져올 수 있다. 제안한 방법이 압축에 강인함을 실험을 통하여 입증하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.344-352
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• 2001

In this paper, we propose a cross-correlation property and a related technique based on the validity of image block in a public watermarking and we embed messages into the high frequency band in the DCT domain because of its imperceptibility and fragility. As a result, we were able to inspect the identity of valid block between error corrected original images and watermarked images through experiments. And we confirmed the viability of this cross-correlation as an application for future public watermarking.

• Journal of Internet Computing and Services
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• v.4 no.3
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• pp.39-46
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• 2003

Generally, the existing watermarking techniques for copyright protection of a digital image are fragile in geometric distortion and all watermark extractions need the same time regardless of degree of distortion. In this paper, we propose the incremental watermarking technique that used a Complex Wavelet Transform(CWT) in order to solve these problems. The proposed incremental watermarking technique embeds a watermark in a phase component after a CWT with an original image, and a watermark is extracted from an watermarked image by stages. A watermark owner can insist on copyright of an image after comparing a correlation between the extracted watermark and the original watermark if it is larger than the threshold. Also, the incremental watermark extraction determines the extraction time of a watermark by the level of distortion. The proposed technique through performance evaluation displayed that it was robust in geometric distortion than the existing watermarking technique.