Jiri Fridrich

Bio: Jiri Fridrich is an academic researcher from Binghamton University. The author has contributed to research in topics: Confusion and diffusion & Square (algebra). The author has an hindex of 3, co-authored 4 publications receiving 1648 citations.

Symmetric Ciphers Based on Two-Dimensional Chaotic Maps

Abstract: In this paper, methods are shown how to adapt invertible two-dimensional chaotic maps on a torus or on a square to create new symmetric block encryption schemes. A chaotic map is first generalized by introducing parameters and then discretized to a finite square lattice of points which represent pixels or some other data items. Although the discretized map is a permutation and thus cannot be chaotic, it shares certain properties with its continuous counterpart as long as the number of iterations remains small. The discretized map is further extended to three dimensions and composed with a simple diffusion mechanism. As a result, a symmetric block product encryption scheme is obtained. To encrypt an N×N image, the ciphering map is iteratively applied to the image. The construction of the cipher and its security is explained with the two-dimensional Baker map. It is shown that the permutations induced by the Baker map behave as typical random permutations. Computer simulations indicate that the cipher has g...

Secure Steganographic Methods for Palette Images

Abstract: In this paper, we study non-adaptive and adaptive steganographic techniques for images with low number of colors in palette image formats. We have introduced the concept of optimal parity assignment for the color palette and designed an efficient algorithm that finds the optimal parity assignment. The optimal parity is independent of the image histogram and depends only on the image palette. Thus, it can be used for increasing the security of steganographic techniques that embed message bits into the parity of palette colors. We have further developed two adaptive steganographic methods designed to avoid areas of uniform color and embed message bits into texturerich portions of the cover image. Both techniques were tested on computer generated images with large areas of uniform color and with fonts on uniform background. No obvious artifacts were introduced by either technique. The last, embedding-while-dithering, technique has been designed for palette images obtained from true color images using color quantization and dithering. In this technique, both the color quantization error and the error due to message embedding are diffused through the image to avoid introducing artifacts inconsistent with the dithering algorithm.

Robust Digital Watermarking Based on Key-Dependent Basis Functions

Abstract: In this paper, we introduce the concept of key-dependent basis functions and discuss its applications to secure robust watermarking for copyright protection and to designing secure public black-box watermark detectors. The new schemes overcome a possible security weakness of global, non-adaptive schemes that apply watermark patterns spanned by a small number of publicly known basis functions. The watermark is embedded into the projections of an image onto the secret set of key-dependent functions (patterns). The robustness of the watermarking scheme with respect to filtering, lossy compression, and combinations of many other attacks is studied. Finally, we propose a candidate for a watermarking scheme that enables the construction of a secure public watermark detector.

Digital Watermarking

Abstract: Digital watermarking is a key ingredient to copyright protection. It provides a solution to illegal copying of digital material and has many other useful applications such as broadcast monitoring and the recording of electronic transactions. Now, for the first time, there is a book that focuses exclusively on this exciting technology. Digital Watermarking covers the crucial research findings in the field: it explains the principles underlying digital watermarking technologies, describes the requirements that have given rise to them, and discusses the diverse ends to which these technologies are being applied. As a result, additional groundwork is laid for future developments in this field, helping the reader understand and anticipate new approaches and applications.

A symmetric image encryption scheme based on 3D chaotic cat maps

Abstract: Encryption of images is different from that of texts due to some intrinsic features of images such as bulk data capacity and high redundancy, which are generally difficult to handle by traditional methods. Due to the exceptionally desirable properties of mixing and sensitivity to initial conditions and parameters of chaotic maps, chaos-based encryption has suggested a new and efficient way to deal with the intractable problem of fast and highly secure image encryption. In this paper, the two-dimensional chaotic cat map is generalized to 3D for designing a real-time secure symmetric encryption scheme. This new scheme employs the 3D cat map to shuffle the positions (and, if desired, grey values as well) of image pixels and uses another chaotic map to confuse the relationship between the cipher-image and the plain-image, thereby significantly increasing the resistance to statistical and differential attacks. Thorough experimental tests are carried out with detailed analysis, demonstrating the high security and fast encryption speed of the new scheme.

Symmetric Ciphers Based on Two-Dimensional Chaotic Maps

Abstract: In this paper, methods are shown how to adapt invertible two-dimensional chaotic maps on a torus or on a square to create new symmetric block encryption schemes. A chaotic map is first generalized by introducing parameters and then discretized to a finite square lattice of points which represent pixels or some other data items. Although the discretized map is a permutation and thus cannot be chaotic, it shares certain properties with its continuous counterpart as long as the number of iterations remains small. The discretized map is further extended to three dimensions and composed with a simple diffusion mechanism. As a result, a symmetric block product encryption scheme is obtained. To encrypt an N×N image, the ciphering map is iteratively applied to the image. The construction of the cipher and its security is explained with the two-dimensional Baker map. It is shown that the permutations induced by the Baker map behave as typical random permutations. Computer simulations indicate that the cipher has g...

Some basic cryptographic requirements for chaos-based cryptosystems

Abstract: In recent years, a large amount of work on chaos-based cryptosystems have been published. However, many of the proposed schemes fail to explain or do not possess a number of features that are fundamentally important to all kind of cryptosystems. As a result, many proposed systems are difficult to implement in practice with a reasonable degree of security. Likewise, they are seldom accompanied by a thorough security analysis. Consequently, it is difficult for other researchers and end users to evaluate their security and performance. This work is intended to provide a common framework of basic guidelines that, if followed, could benefit every new cryptosystem. The suggested guidelines address three main issues: implementation, key management and security analysis, aiming at assisting designers of new cryptosystems to present their work in a more systematic and rigorous way to fulfill some basic cryptographic requirements. Meanwhile, several recommendations are made regarding some practical aspects of analog chaos-based secure communications, such as channel noise, limited bandwith and attenuation.