authentication

Watermarking security has emerged in the last years as as a new subject in the watermarking area. As it brings new challenges to the design of watermarking systems, a good understanding of the problem is fundamental. This paper is intended to clarify the concepts related to watermarking security, provide an exhaustive literature overview, and serve as a starting point for newcomers interested in carrying out research on this topic.

Many image authentication systems in the DCT domain rely on the two invariant properties of the JPEG compression algorithm, which were found out by Lin and Chang. Based on these two assumptions, the authors of these authentication systems utilize that lossy JPEG compression to a pre-defined quality factor always yields the same relationships of coefficients, which can be used to generate image content dependent signature information. In this paper, we prove that this commonly used signature generation for an authentication purpose is not secure. If someone is intended to replace this signature generation by a cryptographically secure hash-based one, then the JPEG properties really have to be invariant. We show that a considerable amount of bit fluctuations can occur caused by rounding and clipping errors due to JPEG compression, which have to be taken into account. The statement of the invariants of the JPEG compression does not hold always. We determine the distribution of coefficient fluctuations and suggest using an extended secure hashbased signature generation in conjunction with error correction coding to overcome these fluctuations. KEY WORDS Secure hash-based image authentication, invariant JPEG properties, coefficient alterations, error correction coding 1.

Abstract—Authentication is the process where claims of identity are verified. Most mechanisms of authentication (e.g., digital signatures and certificates) exist above the physical layer, though some (e.g., spread-spectrum communications) exist at the physical layer often with an additional cost in bandwidth. This paper introduces a general analysis and design framework for authentication at the physical layer where the authentication information is transmitted concurrently with the data. By superimposing a carefully designed secret modulation on the waveforms, authentication is added to the signal without requiring additional bandwidth, as do spread-spectrum methods. The authentication is designed to be stealthy to the uninformed user, robust to interference, and secure for identity verification. The tradeoffs between these three goals are identified and analyzed in block fading channels. The use of the authentication for channel estimation is also considered, and an improved bit-error rate is demonstrated for time-varying channels. Finally, simulation results are given that demonstrate the potential application of this authentication technique. Index Terms—Authentication, modulation, superimposed signaling, watermarking. I.

Abstract. Broadcasting companies have started to move towards a tapeless production process by storing their multimedia (MM) content in a digital archive [1, 2]. Such a digital archive enables a much more efficient production process, and facilitates the disclosure to the general public, allowing broadcasting companies to extend their business model; this comprises extra services such as subscriptions for libraries to access content, pay-per-view for the general public to access its archive, etc. This paper describes our work within the scope of a multidisciplinary project with as goal to design and implement a digital multimedia content archive. We have studied the security aspects of an archive that can be integrated into the production process, allowing broadcasters to share and exchange multimedia content easily, and can be disclosed to semi- and non-professional users. The main result of this study is the identification of security techniques required for such an archive, how they should be embedded into the architecture, and the assessment of their applicability and maturity, based on an extensive threat analysis. 1

Abstract—Because of the great advance in multimedia technology, digital multimedia is vulnerable to malicious manipulations. In this paper, a public key self-recovery block-based video authentication technique is proposed which can not only precisely localize the alteration detection but also recover the missing data with high reliability. In the proposed block-based technique, multiple description coding MDC is used to generate two codes (two descriptions) for each block. Although one block code (one description) is enough to rebuild the altered block, the altered block is rebuilt with better quality by the two block descriptions. So using MDC increases the ratability of recovering data. A block signature is computed using a cryptographic hash function and a doubly linked chain is utilized to embed the block signature copies and the block descriptions into the LSBs of distant blocks and the block itself. The doubly linked chain scheme gives the proposed technique the capability to thwart vector quantization attacks. In our proposed technique, anyone can check the authenticity of a given video using the public key. The experimental results show that the proposed technique is reliable for detecting, localizing and recovering the alterations. Keywords—Authentication, hash function, multiple description coding, public key encryption, watermarking. I.

multimedia security problems