Bull, DR

Canagarajah, CN

Knowles, HD

Winne, DA

English

The widespread adoption of digital video techniques has generated a requirement for authenticity verification in applications such as criminal evidence, insurance claims and commercial databases. The paper investigates the performance, effectivity and efficiency of a spatial digital watermark designed for video authentication. The embedded watermark is estimated from the possible tampered frame with the use of a temporal filter and the motion information. The imperceptible digital stamp is robustly embedded prior to encoding (compression) and allows tamper characterisation of time-base attacks. The functionality of this system is evaluated within an MPEG-4 implementationThe widespread adoption of digital video techniques has generated a requirement for authenticity verification in applications such as criminal evidence, insurance claims and commercial databases. The paper investigates the performance, effectivity and efficiency of a spatial digital watermark designed for video authentication. The embedded watermark is estimated from the possible tampered frame with the use of a temporal filter and the motion information. The imperceptible digital stamp is robustly embedded prior to encoding (compression) and allows tamper characterisation of time-base attacks. The functionality of this system is evaluated within an MPEG-4 implementatio

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                          Winne, D. A., Knowles, H. D., Bull, D. R., & Canagarajah, C. N. (2003). Aninvestigation of an MPEG-4 embedded spatial digital watermark developedfor tamper detection and characterization. In IEEE International Conferenceon Consumer Electronics (ICCF 2003) Los Angeles, CA, USA. (pp. 64 - 65).Institute of Electrical and Electronics Engineers (IEEE).10.1109/ICCE.2003.1218809Link to published version (if available):10.1109/ICCE.2003.1218809Link to publication record in Explore Bristol ResearchPDF-documentUniversity of Bristol - Explore Bristol ResearchGeneral rightsThis document is made available in accordance with publisher policies. Please cite only the publishedversion using the reference above. Full terms of use are available:http://www.bristol.ac.uk/pure/about/ebr-terms.htmlTake down policyExplore Bristol Research is a digital archive and the intention is that deposited content should not beremoved. However, if you believe that this version of the work breaches copyright law please contactopen-access@bristol.ac.uk and include the following information in your message:• Your contact details• Bibliographic details for the item, including a URL• An outline of the nature of the complaintOn receipt of your message the Open Access Team will immediately investigate your claim, make aninitial judgement of the validity of the claim and, where appropriate, withdraw the item in questionfrom public view.TUPM 6.7 AN INVESTIGATION OF AN MPEG-4 EMBEDDED SPATIAL DIGITAL WATERMARK DEVELOPED FOR TAMPER DETECTION AND CHARACTERIZATION D.A. Winne, H.D. Knowles,D.R. Bull andC.N.  Canagarajah University of Bristol, Centre for Communications Research, Merchant Venturers Building, Woodland Road, Bristol, BS8 IUB, UK ABSTRACT The widespread adoption of digital video techniques has generated a requirement for authenticity verification in applications such as criminal evidence, insurance claims and  commercial databases. This paper investigates the performance, effectivity and efficiency of a spatial digital watermark designed for video authentication. The embedded watermark is estimated from the possible tampered frame with the use of a temporal filter and  the motion information. The  imperceptible digital stamp is robustly embedded prior to encoding (compression) and  allows tamper characterisation of time-base attacks. The functionality of this system within an  MPEG-4 implementation is evaluated. INTRODUCTION The vision of cameras watching your every move is close to becoming a reality, with analysts predicting a tenfold increase in CCTV in UK in the next five years [I]. Spy cameras [21 designed to target school vandals or catch burglars [3] have become a reality. Authentication has always been an impoltant issue throughout history 141. Now, in the world of digital imagery and video, the a d  of digital watermarks has made it more accessible. Fragile watermarks designed to detect and locate subtle modification in images have proven useful for authentication (see [SI and [6]), however they lack the ability to provide further information necessary to characterize the attack. This is especially valid for attacks on video signals. Attacks on video signals fall into two categories, [71: The first type covers attacks that tamper with the intensity pattems of the video, e.g. compression, noise, etc. The second type, time-base tampering. disrupts the frame sequencing, e.g. frame cuts, swapping, deletion or foreign frame insertion. It is not straightforward to apply an image watermarhng scheme on a video system as a video system is more than an ordered collection of images. Hybrid video compression systems encode each frame of a sequence differentially. There are temporal and stop frame visibility issues. There is a possibility of reference frame information leakage and often real-time application constraints apply. 0-7803-7721-4l03 $17.00 0 2003 IEEE 64 VIDEO WATERMARKING SYSTEM The system designed to detect and characterise time-base attacks was initially described in [SI, further refined in [IO], and is embedded in a standard MPEG-4 codec. The watermark, shaped by a well-known texture masking function [9], is embedded by signal adaptive addition in the spatial domain, avoiding the need for a drift compensation system: y = x + c m  (1) where a represents the overall strength factor and is linked to the peak signal to noise ratio between the previous encoded frame and its original. This adapts the watermark strength to bit-rate variations. An  estimate of the embedded watermark is generated as follows: where is a estimate of the original frame x and is a de- noised representation of the watermarked and possibly tampered frame 9 The reference frame watermark leakage distortion is circumvented by embedding the same static watermark in low motion (often background) area of subsequent P-frames and by adapting B dynamic watermark per frame in  the active regions. The mean absolute difference between two adjacent frame in combination with a threshold differentiates between the static and dynamic area. The dynamic watermark extraction procedure combines a temporal filter with the motion information. The estimate of the static watermark from each individual frame is merged together to form an improved estimate. The similarity between the extracted and embedded watermark is measured with normalised correlation. The watermark payload depends on the activity and bit-rate of the sequence. The extracted information can be utilized to differentiate between rate-controlled or illicit frame skipping. The static watermark allows detection of GOP deletion and contains global information such as bit-rate, number of skipped frames in previous GOP or time information. Authorized licensed use limited to: UNIVERSITY OF BRISTOL. Downloaded on February 2, 2009 at 08:58 from IEEE Xplore.  Restrictions apply.The dynamic watermark maintains a unique frame based watermark and allows detection of inter GOP tampering such as frame removal. m e  extracted information forms a measure for the authenticity of the sequence. EVALUATION The Receiver Operating Characteristic (ROC) allows us to compare the performance of different watermarking systems. It displays the probability of false positive, F,,' in function of the probability of false negative. F,!. One estimates F, and F,, by calculating the surface under the model distribution with the boundaries set to I-irti TI, where 7' represents the detection threshold. F,, is estimated by assuming that the watermark is drawn from a radially symmetric distribution [ I  I]. F ,  is estimated by assuming that the normalised correlation between the extracted wtermark and the embedded watermark c m  be modelled paramctrically as a bimodal Gaussian Mixture model. The ideal ROC should lie as close as possible to the axes. with F,=F,,=O. Figure I displays the ROC of the dynamic watermark of the Sile111 test sequence. The left solid black graph indicates the trade-off between Fp and Fn when the watermarked scquence is compressed at IMbps. The 4 graphs on the right illustrated the performance decline when the watermarked and encoded sequence is subsequently re-encoded (transcoded) at a bit-rate of IMbps,  5 /2kbpr ,  256kbps and l?dkbps. Even though the sequence was encoded again at lMbps,  the non-linear performance of the quantizer and the different quantizalion step-sires increases the frame distortion. This influences the estimate of the embedded watermark. which results in an increase of F,, for a given F,? Transcoding at a lower bit-rate decreases the performance rapidly. CONCLUSIONS This papcr describes in deplh the technical design, implementation issues and capabilities of a video watermarking system. The system reliably extracts information embedded in the spatial domain and utilises this to measure the authenticity and characterise tampering scenerios. The performance is examined in an MPEG-4 environment with a Receiver Operating Characteristic. The efficiency of the system is compared with other reported video authentication systems. The effectivity is evaluated with the use of different time-base tampering scenarios. REFERENCES Waching your every move. Thursday. 7 February 2W2. BBC News Online. hap:iinewr.bbc.co.uWlihiisci/techil789 I57.rlm Spy cnmeru "'get schml usndds. Wcdnerday 5 June 2002 BBC News. Online hrtp:ilnewr.bbc.co.uWi/hiiscikchn016772r Spy c ~ r r ~ r e s  catch burglars. Tuesday 17 December 2002. BBC News Onlinc, http:linewr bbc.co.uWiihiienglandnSR2495rtm F. Hartung and M. Kulfcr. "Multimedia w a t c m k i n g  techniques." IEEE Pmrurdinp. Val. 87, No. 7, pp. 1076-1 107 July 1999. U. A. Winne, H. U. Knowles. U. R. Bull. C. N. Cuagarajah. "Compression Compatible Digirnl W a t e m r k  algorithm for Authenticity Verification nnd Localization". SPlE confrrmcu: Sur-unry a d  Watrrmorkiny of Mulrimrdio Conrrnri IV, 2W1. San Jose. paper-ID: 4675-38 U. A. Winnc. H. D. K B O W ~ E .  U  R. Bull. C. N .  Cunugarajrh, "Digiral Watermuking in Wavelet Domain with Prtdirtortion for Authenticity Vcrificvtion ;urd Localization", SPlE confirenre: Srcurri). end Woierm~ikiny r,l Muirimrdio Cunienrr IV. 2WI. San Jose. paper-tu: 4675-39 B. C. Mobsrreri. M. J. Sieffen and R. J. Simard. Tonlcnt iluthen~icntion .and tamper detection in digital video," IEEE h i 7  Dominique A. Winne. Henry U. Knowlcs, David R. Buli. C. Nishan Cilnugmjh, "Spalrd digital watermark far MPEG-2 video authenricution 2nd tamper detection", IEEE Inrm"ionol Conference on ACOU.U~CI. Sprrrh and Si& Prore.~rins. 0rl;mdo-Floridu. pp 3457-3460, May 13-17. S.Yolorhynovrkiy. A.Herrige1. N.Baumgmltner and T.Pun. "A slo~hilstic approzilch lo comnt adaptivc digilvi image WillemnrkinE". in lnternalional Workshm on Lnformarion Hiding, c~nf on IWC prOr.. v ~ c o ~ ~ ~ ~ ,  paper m:1973. sep$. zwo. Dresden. Gcrmmy. , Lecture Norer in Computer Science. Ed. Andress Pfilzmnn, pp. 21 1-236. 29 September - I OEtaber. 1999. I 101 Dominique A. Winne. Henry U. Knowler. David R. Bull, C. Nishan C;msg;uajah "An Efficient MPEG-4 video authentication scheme with temporal filtering". submitted for lntemational Conference on Signal Processing, 2M3 Barcelonu I1 I I  M. I. Miller and J. A. Bloom. "Computing .the Probability of Fatre Watermuk Uetecti~n". Proceedings of the Third tulemvti~nrl Workshop in Informtion Hiding. pp 146-158. 1999 65 Authorized licensed use limited to: UNIVERSITY OF BRISTOL. Downloaded on February 2, 2009 at 08:58 from IEEE Xplore.  Restrictions apply.

2W2. BBC News Online. hap:iinewr.bbc.co.uWlihiisci/techil789 I57.rlm Spy cnmeru &quot;'get schml usndds.

I OEtaber.

N.Baumgmltner and T.Pun. &quot;A slo~hilstic approzilch lo comnt adaptivc digilvi image WillemnrkinE&quot;.

Nishan C;msg;uajah &quot;An Efficient MPEG-4 video authentication scheme with temporal filtering&quot;. submitted for lntemational

An investigation of an MPEG-4 embedded spatial digital watermark developed for tamper detection and characterization

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An investigation of an MPEG-4 embedded spatial digital watermark developed for tamper detection and characterization

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