Fraunhofer Institut für Integrierte Publikations-und Informationssysteme IPSI

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  • Publication
    Using entropy for image and video authentication watermarks
    ( 2006)
    Thiemert, S.
    ;
    Sahbi, H.
    ;
    Steinebach, M.
    There are several scenarios where the integrity of digital images and videos has to be verified. Examples can be found in videos captured by surveillance cameras. In this paper we propose a semi-fragile watermarking scheme, which can be applied on still images as well as on digital videos. We concentrate on the protection of I-frames in compressed MPEG-1/2 videos. We use the entropy of the probability distribution of gray level values in block groups to generate a binary feature mask, which is embedded robustly into an adjacent I-frame. The approach can distinguish between content-preserving and content-changing manipulations. Positions of content-changing manipulations can be localized. We provide experimental results to analyze the effectiveness of the scheme. In the evaluation part we concentrate on the robustness against content-preserving and the sensitivity to content-changing manipulations.
  • Publication
    A digital watermark for vector-based fonts
    ( 2006)
    Thiemert, S.
    ;
    Steinebach, M.
    ;
    Wolf, P.
    In this paper we present a blind watermarking scheme for vector-based fonts. The scheme can be used for authenticating the copyright holder as well as for identifying customers of fonts. We slightly modify the symmetry between curve pairs to embed a binary message. The watermark is invisible and robust against conversion into other vector-based font formats. An implementation for TrueType-Fonts was evaluated by typeface designers. Based on the blind watermarking scheme we discuss an extension to a non-blind watermark, which is in addition robust against uniform scaling.
  • Publication
    Applying interest operators in semi-fragile video watermarking
    ( 2005)
    Thiemert, S.
    ;
    Sahbi, H.
    ;
    Steinebach, M.
    In this article we present a semi-fragile watermarking scheme for authenticating intra-coded frames in compressed digital videos. The scheme provides the detection of content-changing manipulations while being moderately robust against content-preserving manipulations. We describe a watermarking method based on invariant features referred to as interest points. The features are extracted using the Moravec-Operator. Out of the interest points we generate a binary feature mask, which is embedded robustly as watermark into the video. In the verification process we compare the detected watermark with the interest points from the video to be verified. We present test results evaluating the robustness against content-preserving manipulations and the fragility in terms of content-changing manipulations. Beside the discussion of the results we propose a procedure to provide security of the scheme against forgery attacks.
  • Publication
    Synchronization techniques to detect MPEG video frames for watermark retrieval
    ( 2004)
    Hauer, E.
    ;
    Thiemert, S.
    A main problem of I-frame based watermarking schemes is their lack of robustness regarding re-encoding attacks on MPEG material. After a normal post-processing modification the structure of the Groups of Pictures (GOPs) in the modified video should be the same as in the original one. An attack, which has the goal to destroy the watermark, could change this structure. The position of the marked intra coded frames will be shifted. Without detecting the correct frame position an incorrect watermark message could be retrieved. Our conceptual paper proposes a possible solution. A combined watermark, consisting of two watermark messages, is embedded into the video material to increase the robustness of the watermark. The first part of the message is the synchronization information to locate the previously marked frames. The second part contains the information watermark. Our approach is to design a template pattern based on the synchronization information. With the pattern th e original I-frame can be detected and the correct watermark information can be retrieved. After the recovery of the attacked video material the watermark can be correctly retrieved. We present the concept and the evaluation of the first test results.
  • Publication
    A feature-watermarking scheme for JPEG image authentication
    ( 2004)
    Wang, J.S.
    ;
    Dai, Y.W.
    ;
    Thiemert, S.
    ;
    Wang, Z.Q.
    Feature-based watermark is a special kind of watermark, which reflects the features of the content, and these features are deliberately chosen in the way that they will keep invariant during "content preserving" modifications while being sensitive to "malicious" attacks. In this paper, a novel approach to content authentication for JPEG images is proposed. The image authentication method is based on partial energy relation between groups of 8x8 DCT blocks as features, while the strategies of watermark embedding and extraction is based on improved DEW algorithm. Our proposed scheme has the capability of differentiating "content preserving" modifications from "malicious" attacks and so can ascertain and locate the "malicious" attacks. Experimental results show the feasibility of the proposed scheme.
  • Publication
    A high-capacity block based video watermark
    ( 2004)
    Thiemert, S.
    ;
    Vogel, T.
    ;
    Dittmann, J.
    ;
    Steinebach, M.
  • Publication
    Digitale Wasserzeichen als Träger von Metainformation für Geographische Informationssysteme
    ( 2004)
    Thiemert, S.
    ;
    Liu, H.
    ;
    Rauch, M.
    ;
    Pfannkuche, R.
    ;
    Fahrion, R.
    ;
    Steinebach, M.
  • Publication
    Feature-based watermarking scheme for MPEG-I/II video authentication
    ( 2004)
    Dai, Y.
    ;
    Thiemert, S.
    ;
    Steinebach, M.
    This paper presents a new content-fragile watermarking algorithm for the detection and localization of malicious manipulations of MPEG-I/II videos. While being fragile to malicious manipulations, the watermarking scheme is robust against content-preserving manipulations like re-encoding processes. It is a bitstream watermarking method based on 8×8 DCT blocks. One of the main advantages of our scheme is the possibility of localizing positions within the video where modifications occurred. Another main advantage is the portability of the scheme to other multimedia documents based on the 8×8 DCT block domain, e.g. JPEG images. The framework of the watermarking scheme can be divided into three main parts: watermark construction, watermark embedding and watermark detection. We derive a Content Based Message (CBM) from the multimedia document, based on a partial energy relationship between two groups of DCT blocks. Embedding the CBM is based on the Differential Energy Waterma rking (DEW) concept. In the detection process we compare the CBM and the retrieved watermark to detect and locate manipulations. Besides the algorithm we present experimental results to demonstrate the feasibility of the scheme. We discuss four experiments representing four typical kinds of malicious manipulations.
  • Publication
    Authentication of MPEG-4 data: Risks and solutions
    ( 2003)
    Lang, A.
    ;
    Thiemert, S.
    ;
    Hauer, E.
    ;
    Liu, H.
    ;
    Petitcolas, F.A.P.
    MPEG-4 is an international object-based standard that provides technological basis for digital television, interactive graphics and multimedia applications. These objects can be natural or synthetic e.g. textures, 3D objects, videos or sounds. In this paper we suggest an integrity approach to protect the content of MPEG-4 data. The essential part of this approach is to embed a robust watermark into each visual, audio and 3D object. The content fragile watermark verifying the integrity of a scene is the sum of all information retrieved from the robust watermarks extracted from the objects of the scene. The information of the fragile watermark will be distributed redundantly to all robust watermarks of the scene. Another essential part of our approach is to embed a part of the scene description or object descriptors as a watermark message into the video or audio streams. The amount of embedded information depends on the payload of the watermarking algorithms. We also anal yze the possibility of embedding equivalent information into 3D models, depending on the application.
  • Publication
    Ausgewählte Angriffe der Stirmark Benchmark Suite
    ( 2002)
    Lang, A.
    ;
    Thiemert, S.
    ;
    Steinebach, M.
    ;
    Dittmann, J.