There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Watermarking embeds information into a digital signal like audio, image, or video. Reversible image watermarking can restore the original image without any distortion after the hidden data is extracted. In this paper, we present a novel reversible watermarking scheme using an interpolation technique, which can embed a large amount of covert data into images with imperceptible modification. Different from previous watermarking schemes, we utilize the interpolation-error, the difference between interpolation value and corresponding pixel value, to embed bit ?1? or ?0? by expanding it additively or leaving it unchanged. Due to the slight modification of pixels, high image quality is preserved. Experimental results also demonstrate that the proposed scheme can provide greater payload capacity and higher image fidelity compared with other state-of-the-art schemes.

Reversible Image Watermarking Using Interpolation Technique

Disclosed herein are methods and systems for encoding digital watermarks into content signals. Also disclosed are systems and methods for detecting and/or verifying digital watermarks in content signals. According to one embodiment, a system for encoding of digital watermark information includes: a window identifier for identifying a sample window in the signal; an interval calculator for determining a quantization interval of the sample window; and a sampler for normalizing the sample window to provide normalized samples. According to another embodiment, a system for pre-analyzing a digital signal for encoding at least one digital watermark using a digital filter is disclosed. According to another embodiment, a method for pre-analyzing a digital signal for encoding digital watermarks comprises: (1) providing a digital signal; (2) providing a digital filter to be applied to the digital signal; and (3) identifying an area of the digital signal that will be affected by the digital filter based on at least one measurable difference between the digital signal and a counterpart of the digital signal selected from the group consisting of the digital signal as transmitted, the digital signal as stored in a medium, and the digital signal as played backed. According to another embodiment, a method for encoding a watermark in a content signal includes the steps of (1) splitting a watermark bit stream; and (2) encoding at least half of the watermark bit stream in the content signal using inverted instances of the watermark bit stream. Other methods and systems for encoding/decoding digital watermarks are also disclosed.

Optimization methods for the insertion, protection, and detection of digital watermarks in digitized data

With the increasing importance of images in people’s daily life, content-based image retrieval (CBIR) has been widely studied. Compared with text documents, images consume much more storage space. Hence, its maintenance is considered to be a typical example for cloud storage outsourcing. For privacy-preserving purposes, sensitive images, such as medical and personal images, need to be encrypted before outsourcing, which makes the CBIR technologies in plaintext domain to be unusable. In this paper, we propose a scheme that supports CBIR over encrypted images without leaking the sensitive information to the cloud server. First, feature vectors are extracted to represent the corresponding images. After that, the pre-filter tables are constructed by locality-sensitive hashing to increase search efficiency. Moreover, the feature vectors are protected by the secure kNN algorithm, and image pixels are encrypted by a standard stream cipher. In addition, considering the case that the authorized query users may illegally copy and distribute the retrieved images to someone unauthorized, we propose a watermark-based protocol to deter such illegal distributions. In our watermark-based protocol, a unique watermark is directly embedded into the encrypted images by the cloud server before images are sent to the query user. Hence, when image copy is found, the unlawful query user who distributed the image can be traced by the watermark extraction. The security analysis and the experiments show the security and efficiency of the proposed scheme.

A Privacy-Preserving and Copy-Deterrence Content-Based Image Retrieval Scheme in Cloud Computing

Garbled circuits, a classical idea rooted in the work of Yao, have long been understood as a cryptographic technique, not a cryptographic goal. Here we cull out a primitive corresponding to this technique. We call it a garbling scheme. We provide a provable-security treatment for garbling schemes, endowing them with a versatile syntax and multiple security definitions. The most basic of these, privacy, suffices for two-party secure function evaluation (SFE) and private function evaluation (PFE). Starting from a PRF, we provide an efficient garbling scheme achieving privacy and we analyze its concrete security. We next consider obliviousness and authenticity, properties needed for private and verifiable outsourcing of computation. We extend our scheme to achieve these ends. We provide highly efficient blockcipher-based instantiations of both schemes. Our treatment of garbling schemes presages more efficient garbling, more rigorous analyses, and more modularly designed higher-level protocols.

/pdf/foundations-of-garbled-circuits-f3gqwxe1v8.pdf

Foundations of garbled circuits

We formalize a new attack model for collusion secure codes, incorporating attacks on the underlying watermarking scheme as well as cut-and-paste attacks traditionally considered for collusion secure codes. We use this model to analyze the collusion resistance of two versions of the Tardos code, both for binary and nonbinary alphabets. The model allows us to consider different signal processing attacks on the content, namely the addition of noise and averaging attacks. The latter may result in content segments that have multiple watermarks embedded. We study two versions of the q-ary Tardos code in which the accusation method has been modified so as to allow for the detection of multiple symbols in the same content segment. We show that both variants yield efficient codes in the new model, parametrized for realistic attacker strengths.

/pdf/tardos-fingerprinting-codes-in-the-combined-digit-model-4kluylbads.pdf

Tardos fingerprinting codes in the combined digit model

A system (500) for cryptographic processing of content comprises an input (502) for receiving the content (566). A plurality of look-up tables (504) represents a white- box implementation of a combined cryptographic and watermarking operation (460). The look-up tables represent processing steps of the combined cryptographic and watermarking operation and the look-up tables being arranged for being applied according to a predetermined look-up scheme. The look-up scheme prescribes that an output of a first look¬ up table of the plurality of look-up tables be used to generate an input of a second look-up table of the plurality of look-up tables. The combined cryptographic and watermarking operation comprises a cryptographic operation and a watermarking operation. A control module (512) looks up values in the plurality of look-up tables in dependence on the received content and in accordance to the look-up scheme, thereby applying the combined cryptographic and watermarking operation to the content.

Cryptographic processing of content

We introduce a new attack model for collusion-secure codes, called the combined digit model, which represents signal processing attacks against the underlying watermarking level better than existing models. In this paper, we analyze the performance of two variants of the Tardos code and show that both variants can accommodate the new model and resist collusion attacks with only a modest increase in code length as compared to the results for the commonly used restricted digit model.

Tardos Fingerprinting Codes in the Combined Digit Model (Extended Abstract)

The invention relates to embedding auxiliary data in the form of a multibit payload in a host signal, and encrypting the associated detection key. Moreover, the invention relates to extracting the auxiliary data in the form of the multibit payload from a data signal. Auxiliary data is embedded in a host signal by the following steps. First a reference watermark is provided, subsequently an encrypted detection key associated only with the reference watermark is generated. The encrypted detection key may be a scrambled version of the watermark. In a further step, the multibit watermark is generated and a multibit payload is encoded into the reference watermark. Finally, the multibit watermark is embedded into the host signal.

Multibit forensic watermark with encrypted detection key

In an electronic content distribution system, it is preferable to embed forensic tracking watermarks at the client-side to limit bandwidth usage and server complexity. Embedding in these untrusted clients, however, requires secure embedding methods that do not leak unmarked contents or the watermarking secrets. In this work, we propose a look-up-table (LUT) based cipher, similar to Andersen's Chameleon cipher, for securely embedding spread-spectrum watermarks, which are noise robust and detectable without the original content. We also develop fast detection mechanisms that make the watermark detection feasible for tracking systems with large number of clients. Our fast detection algorithm improves detection speed six orders of magnitude in a typical system.

Mehmet U. Celik

Papers

Tardos fingerprinting codes in the combined digit model

Cryptographic processing of content

Tardos Fingerprinting Codes in the Combined Digit Model (Extended Abstract)

Multibit forensic watermark with encrypted detection key

Secure Embedding of Spread Spectrum Watermarks using Look-up-Tables