Báo cáo hóa học: Research Article Hierarchical Spread Spectrum Fingerprinting Scheme Based on the CDMA Technique Minoru Kuribayashi (EURASIP Member)

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Báo cáo hóa học: " Research Article Hierarchical Spread Spectrum Fingerprinting Scheme Based on the CDMA Technique Minoru Kuribayashi (EURASIP Member)"Hindawi Publishing CorporationEURASIP Journal on Information SecurityVolume 2011, Article ID 502782, 16 pagesdoi:10.1155/2011/502782Research ArticleHierarchical Spread Spectrum Fingerprinting SchemeBased on the CDMA Technique Minoru Kuribayashi (EURASIP Member) Graduate School of Engineering, Kobe University, 1-1, Rokkodai, Nada, Kobe, Hyogo 657-8501, Japan Correspondence should be addressed to Minoru Kuribayashi, kminoru@kobe-u.ac.jp Received 10 March 2010; Revised 15 December 2010; Accepted 20 January 2011 Academic Editor: Jeffrey A. Bloom Copyright © 2011 Minoru Kuribayashi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Digital fingerprinting is a method to insert user’s own ID into digital contents in order to identify illegal users who distribute unauthorized copies. One of the serious problems in a fingerprinting system is the collusion attack such that several users combine their copies of the same content to modify/delete the embedded fingerprints. In this paper, we propose a collusion-resistant fingerprinting scheme based on the CDMA technique. Our fingerprint sequences are orthogonal sequences of DCT basic vectors modulated by PN sequence. In order to increase the number of users, a hierarchical structure is produced by assigning a pair of the fingerprint sequences to a user. Under the assumption that the frequency components of detected sequences modulated by PN sequence follow Gaussian distribution, the design of thresholds and the weighting of parameters are studied to improve the performance. The robustness against collusion attack and the computational costs required for the detection are estimated in our simulation.1. Introduction linear averaging strategy is the most damaging one [6]. It is important to generate fingerprints that can identifyAccompanying technology advancement, multimedia con- the colluders. A number of works on designing collusion-tent (audio, image, video, etc.) has become easily available resistant fingerprints have been proposed. Many of themand accessible. However, such an advantage also causes a can be categorized into two approaches. One approach isserious problem that unauthorized users can duplicate digital to exploit the spread spectrum (SS) technique [2–5], andcontent and redistribute it. In order to solve this problem, the other approach is to devise an exclusive code, known asdigital fingerprinting is used to trace the illegal users, where collusion-secure code [7–12], which can trace colluders.a unique ID known as a digital fingerprint [1] is embedded In the former approach, spread spectrum sequences,into the content assisted by a watermarking technique before which follow a normal distribution, are assigned to users asdistribution. When a suspicious copy is found, the owner can fingerprints. The origin of the spread spectrum watermark-identify illegal users by extracting the fingerprint. ing scheme is Cox’s method [2] that embeds a sequence into Since each user purchases contents involving his own the frequency components of a digital image and detectsfingerprint, the fingerprinted copy slightly differs with it using a correlator. In this work, the fingerprinting iseach other. Therefore, a coalition of users can combine introduced as a possible application of the spread spectrumtheir different marked copies of the same content for the watermarking. Because of the quasi-orthogonality amongpurpose of removing/changing the original fingerprint. In spread spectrum sequence used in the paper, the identifi-a fingerprinting system, a usual assumption is that the cation of users from an illegal copy is possible. Hereafter,colluders add white Gaussian noise to a forgery which they we use the term “fingerprinting” as the application of thecreate by combining (averaging) their copies in a linear watermarking scheme. Since normally distributed valuesor nonlinear fashion [2–5]. Under the assumption of a allow the theoretical and statistical analysis of the method,fixed correlation detector, it is reported that the uniform mo ...