William Puech

A reversible data hiding method for encrypted images

Since several years, the protection of multimedia data is becoming very important. The protection of this multimedia data can be done with encryption or data hiding algorithms. To decrease the transmission time, the data compression is necessary. Since few years, a new problem is trying to combine in a single step, compression, encryption and data hiding. So far, few solutions have been proposed to combine image encryption and compression for example. Nowadays, a new challenge consists to embed data in encrypted images. Since the entropy of encrypted image is maximal, the embedding step, considered like noise, is not possible by using standard data hiding algorithms. A new idea is to apply reversible data hiding algorithms on encrypted images by wishing to remove the embedded data before the image decryption. Recent reversible data hiding methods have been proposed with high capacity, but these methods are not applicable on encrypted images. In this paper we propose an analysis of the local standard deviation of the marked encrypted images in order to remove the embedded data during the decryption step. We have applied our method on various images, and we show and analyze the obtained results.

Fast Protection of H.264/AVC by Selective Encryption of CAVLC and CABAC for I and P Frames

This paper presents a novel method for the protection of bitstreams of state-of-the-art video codec H.264/AVC. The problem of selective encryption (SE) is addressed along with the compression in the entropy coding modules. H.264/AVC supports two types of entropy coding modules. Context-adaptive variable length coding (CAVLC) is supported in H.264/AVC baseline profile and context-adaptive binary arithmetic coding (CABAC) is supported in H.264/AVC main profile. SE is performed in both types of entropy coding modules of this video codec. For this purpose, in this paper the encryption step is done simultaneously with the entropy coding CAVLC or CABAC. SE is performed by using the advanced encryption standard (AES) algorithm with the cipher feedback mode on a subset of codewords/binstrings. For CAVLC, SE is performed on equal length codewords from a specific variable length coding table. In case of CABAC, it is done on equal length binstrings. In our scheme, entropy coding module serves the purpose of encryption cipher without affecting the coding efficiency of H.264/AVC by keeping exactly the same bitrate, generating completely compliant bitstream and utilizing negligible computational power. Owing to no escalation in bitrate, our encryption algorithm is better suited for real-time multimedia streaming over heterogeneous networks. It is perfect for playback on handheld devices because of negligible increase in processing power. Nine different benchmark video sequences containing different combinations of motion, texture, and objects are used for experimental evaluation of the proposed algorithm.

Visual Protection of HEVC Video by Selective Encryption of CABAC Binstrings

This paper presents one of the first methods allowing the protection of the newly emerging video codec HEVC (High Efficiency Video Coding). Visual protection is achieved through selective encryption (SE) of HEVC-CABAC binstrings in a format compliant manner. The SE approach developed for HEVC is different from that of H.264/AVC in several aspects. Truncated rice code is introduced for binarization of quantized transform coefficients (QTCs) instead of truncated unary code. The encryption space (ES) of binstrings of truncated rice codes is not always dyadic and cannot be represented by an integer number of bits. Hence they cannot be concatenated together to create plaintext for the CFB (Cipher Feedback) mode of AES, which is a self-synchronizing stream cipher for so-called AES-CFB. Another challenge for SE in HEVC concerns the introduction of context, which is adaptive to QTC. This work presents a thorough investigation of HEVC-CABAC from an encryption standpoint. An algorithm is devised for conversion of non-dyadic ES to dyadic, which can be concatenated to form plaintext for AES-CFB. For selectively encrypted binstrings, the context of truncated rice code for binarization of future syntax elements is guaranteed to remain unchanged. Hence the encrypted bitstream is format-compliant and has exactly the same bit-rate. The proposed technique requires very little processing power and is ideal for playback on hand held devices. The proposed scheme is acceptable for DRM of a wide range of applications, since it protects the contour and motion information, along with texture. Several benchmark video sequences of different resolutions and diverse contents were used for experimental evaluation of the proposed algorithm. A detailed security analysis of the proposed scheme verified the validity of the proposed encryption scheme for content protection in a wide range of applications.

Short Communication: Digital image restoration by Wiener filter in 2D case

Modern digital technology has made it possible to manipulate multi-dimensional signals with systems that range from simple digital circuits to advanced parallel computers. The goal of this manipulation can be divided into three categories:*Image Processing image in->image out. *Image Analysis image in->measurements out. *Image Understanding image in->high-level description out. Further, we will restrict ourselves to two-dimensional (2D) image processing although most of the concepts and techniques that are to be described can be extended easily to three or more dimensions. The Wiener filter is a solution to the restoration problem based upon the hypothesized use of a linear filter and the minimum mean-square (or rms) error criterion. In the example given below the image a[m,n] was distorted by a bandpass filter and then white noise was added to achieve an SNR=30dB.

Selective Encryption of Human Skin in JPEG Images

In this study we propose a new approach for selective encryption in the Huffman coding of the discrete cosine transform (DCT) coefficients using the advanced encryption standard (AES). The objective is to partially encrypt the human face in an image or video sequence. This approach is based on the AES stream ciphering using variable length coding (VLC) of the Huffmans vector. The proposed scheme allows the decryption of a specific region of the image and results in a significant reduction in encrypting and decrypting processing time. It also provides a constant bit rate while maintaining the JPEG and MPEG bitstream compliance.

A comprehensive process of reverse engineering from 3D meshes to CAD models

In an industrial context, most manufactured objects are designed using CAD (Computer-Aided Design) software. For visualization, data exchange or manufacturing applications, the geometric model has to be discretized into a 3D mesh composed of a finite number of vertices and edges. However, the initial model may sometimes be lost or unavailable. In other cases, the 3D discrete representation may be modified, e.g. after numerical simulation, and no longer corresponds to the initial model. A retro-engineering method is then required to reconstruct a 3D continuous representation from the discrete one. In this paper, we present an automatic and comprehensive retro-engineering process dedicated mainly to 3D meshes obtained initially by mechanical object discretization. First, several improvements in automatic detection of geometric primitives from a 3D mesh are presented. Then a new formalism is introduced to define the topology of the object and compute the intersections between primitives. The proposed method is validated on 3D industrial meshes.

Fast protection of H.264/AVC by selective encryption of CABAC

This paper presents a novel method for the protection of copyrighted multimedia content. The problem of selective encryption (SE) is being addressed along with the compression for the state of the art video codec H.264/AVC. SE is performed in the context-based adaptive binary arithmetic coding (CABAC) module of video codec. For this purpose, CABAC is converted to an encryption cipher. It has been achieved through scrambling of equal length bin strings. In our scheme, CABAC engine serves the purpose of encryption cipher without affecting the coding efficiency of H.264/AVC by keeping exactly the same bit rate, generating completely compliant bitstream and utilizing negligible computational power. Owing to no escalation in bit rate, our encryption algorithm is better suited for real-time multimedia streaming. It is perfect for playback on handheld devices because of negligible increase in processing power. Nine different benchmark video sequences containing different combinations of motion, texture and objects are used for experimental evaluation of the proposed algorithm.

Considering the reconstruction loop for watermarking of intra and inter frames OF H.264/AVC

This paper presents and analyzes a new approach to data hiding that embeds in both the intra- and inter-frames from the H.264/AVC video codec. Most of the current video data hiding algorithms take into account only the intra-frames for message embedding. This may be attributed to the perception that inter-frames are highly compressed due to the motion compensation, and any embedding message inside these may adversely affect the compression efficiency significantly. Payload of the inter-frames is also thought to be less, compared with the intra-frames, because of the lesser residual data. We analyze data hiding in both intra- and inter-frames over a wide range of QP values and observe that the payload of the inter is comparable with that of the intra-frames. Message embedding, in only those non-zero quantized transform coefficients (QTCs) which are above a specific threshold, enables us to detect and extract the message on the decoding side. There is no significant effect on the overall bitrate and PSNR of the video bitstream because instead of embedding message in the compressed bitstream, we have embedded it during the encoding process by taking into account the reconstruction loop. For the non-zero QTCs, in the case of intra-frames, we benefit from the spatial masking, while in the case of inter-frames, we exploit the motion and texture masking. We can notice that the data hiding is done during the compression process and the proposed scheme takes into account the reconstruction loop. The proposed scheme does not target robustness and the obtained payload is higher, with a better trade-off in terms of quality and bitrate, as compared with previous works.

Adaptive steganography by oracle (ASO)

HUGO [1] and MOD [2] are the most secure adaptive embedding algorithms of 2011. These algorithms strive to hide a secret message, while minimizing an ad hoc embedding impact. They use a detectability map, which, if properly defined, is correlated to the security. In this paper, we present a new adaptive embedding scheme: Adaptive Steganography by Oracle (ASO). It is based on an oracle used to calculate the detectability map, and this oracle use the Kodovskýs ensemble classifiers [3]. Our approach preserves both cover image and senders database distributions during the embedding process, which improves the security. In addition, it offers to the sender the opportunity to choose the most reliable image( s), during his secret communication. Experimental results show that our embedding scheme presents good security performances, since the detection error of ASO is much higher than that of HUGO.

Image Encryption and Compression for Medical Image Security

This tutorial presents the problem of protecting the transmission of medical images. The presented algorithms will be applied to images, videos and 3D objects. The main keywords are compression, encryption, watermarking and data hiding.