فایل ورد کامل یک طرح حفاظت از امنیت محتوا در حوزه فشرده شده JPEG

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تعداد صفحات این فایل: ۲۴ صفحه

بخشی از مقاله انگلیسیعنوان انگلیسی:A content security protection scheme in JPEG compressed domain~~en~~

Abstract

The access and distribution convenience of public networks opens a considerable content security threat when sending, receiving, and using multimedia information. In this paper, a content security protection scheme that integrates encryption and digital fingerprinting is proposed to provide comprehensive security protection for multimedia information during its transmission and usage. In contrast to other schemes, this method is implemented in the JPEG compressed domain with no transcoding or decompression, therefore, this scheme is highly efficient and suitable for multimedia information, which is seldom available in an uncompressed form. In addition, a variable modular encryption method is proposed to solve the invalid variable length coding (VLC) problem when a compressed data stream is encrypted directly. Experimental results demonstrate improved security and the efficiency provided by the proposed scheme. The experiments also demonstrate imperceptibility and collusion resistance of fingerprints.

۱ Introduction

With the rapid development of information and communication technologies, it has become commonplace to distribute multimedia information over the internet. However, this data access and distribution convenience increases security risks when sending and receiving sensitive information and images. Eavesdropping, unauthorized duplication, and release are a growing threat which must be effectively contained. In some instances, exposure and leakage of this information will cause damage to personal privacy or even national security. Therefore, effective content security measures must be adopted to guarantee the safety of sensitive or proprietary multimedia information.

Two requirements must be satisfied to guarantee the security of multimedia information, confidentiality and proper usage [1,2,26]. Encryption is a common method for ensuring data confidentiality, but data security after decryption cannot be ensured because the data can be duplicated and distributed improperly by legal users. Fingerprinting is an emerging technology that imperceptibly embeds a unique user-dependent identity number into media content. If users distribute data improperly, the hidden fingerprints can be extracted from the copied media and used to trace unauthorized users. But, when fingerprinting digital data, the problem of collusion attacks must be considered [3]. Colluders compare their fingerprinted copies of data, modify differences and generate a new copy to avoid discovery. However, digital fingerprinting is a passive form of security and works only after the content is received and has been made available to the user [4]. Therefore, only a combination of encryption and fingerprinting can provide comprehensive content security protection for multimedia information, because both confidentiality and proper usage vulnerabilities are addressed.

Several intermediate goals must be achieved to meet the security requirements for multimedia information content protection and are listed as follows:

۱ Encryption security. Different from text/binary encryption, multimedia encryption requires both cryptographic security and perceptual security [5]. The former refers to security against cryptographic attacks, and the latter means that the encrypted multimedia content is unintelligible to human perception.

۲ Format compliance. Format information is generated after encoding multimedia data, such as file headers and synchronization information. This information will be used by the decoder to successfully recover data and to keep multimedia communication synchronized [5]; therefore, format information must not be effected by encryption. The ciphertext is considered format-compliant if the encrypted data stream can be decoded by a standard decoder.

۳ Imperceptibility. The embedded fingerprint information must be invisible and have little perceptual impact on the image quality.

۴ Robustness against collusion attacks. The embedded fingerprint code must be robust against collusion attacks.

۵ Efficiency. Encryption and fingerprinting operations should be highly efficient because multimedia information is huge and the number of users is extremely large. It is widely believed that video information must be distributed efficiently because of its data rate and large size. However, some image information is also massive [15]. For example, a typical hyperspectral remote sensing image covering a small region of a few kilometers contains millions of pixels, and each pixel is represented by several bands [27]. Thus, the data volume can be several GB or even several hundred GB [28].

۶ Compression ratio. In all cases, multimedia encryption algorithms should not change compression ratio or should at least keep the changes in a small range [5].

۷ Compressed domain implementation. Because most multimedia signals are available in a compressed form, it is desirable to encrypt and embed fingerprints directly into the bitstream of compressed media with no transcoding, decompression or even partial versions of such computations [6–۸,۱۵].

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