Writing on wet paper (original) (raw)

Perturbed quantization steganography with wet paper codes

Proceedings of the 2004 multimedia and security workshop on Multimedia and security - MM&Sec '04, 2004

In this paper, we introduce a new approach to passive-warden steganography in which the sender embeds the secret message into a certain subset of the cover object without having to share the selection channel with the recipient. An appropriate informationtheoretical model for this communication is writing in memory with (a large number of) defective cells [1]. We describe a simple variable-rate random linear code for this channel (the "wet paper" code) and use it to develop a new steganographic methodology for digital media files-Perturbed Quantization. In Perturbed Quantization, the sender hides data while processing the cover object with an information-reducing operation, such as lossy compression, downsampling, A/D conversion, etc. The sender uses the cover object before processing as side information to confine the embedding changes to those elements of the processed cover object whose values are the most "uncertain". This informed-sender embedding and uninformed-recipient message extraction improves steganographic security because an attacker cannot easily determine from the processed stego object the location of embedding changes. Heuristic is presented and supported by blind steganalysis [2] that a specific case of Perturbed Quantization for JPEG images is significantly less detectable than current JPEG steganographic methods.

Ensuring Message Embedding in Wet Paper Steganography

Lecture Notes in Computer Science, 2011

Syndrome coding has been proposed by Crandall in 1998 as a method to stealthily embed a message in a cover-medium through the use of bounded decoding. In 2005, Fridrich et al. introduced wet paper codes to improve the undetectability of the embedding by enabling the sender to lock some components of the cover-data, according to the nature of the cover-medium and the message. Unfortunately, almost all existing methods solving the bounded decoding syndrome problem with or without locked components have a non-zero probability to fail. In this paper, we introduce a randomized syndrome coding, which guarantees the embedding success with probability one. We analyze the parameters of this new scheme in the case of perfect codes.

Steganography via codes for memory with defective cells

Steganography is the art of covert (undetectable) communication in which secret data is embedded in innocuous looking messages by slightly modifying them. The detectability of secret data is influenced, besides other factors, by the placement of embedding changes within the message and by the embedding efficiency-the number of bits embedded per one embedding change. In this paper, we first show that codes for memory with defective cells enable steganographic communication without sharing the placement of embedding changes. This allows construction of a new class of steganographic schemes with improved security. We then describe an efficient coding method for memory with defective cells based on the LT process that is suitable for steganographic applications. In the second part of the paper, we explore a different approach based on random linear codes on small blocks with the goal to decrease the number of embedding changes. The embedding efficiency of this approach is compared to theoretically achievable bounds.

Abstract Information Hiding: Steganography and

2008

The goal of steganography is to insert a message into a carrier signal so that it cannot be detected by unintended recipients. Due to their widespread use and availability of bits that can be changed without perceptible damage of the original signal images, video, and audio are widespread carrier media. Steganalysis attempts to discover hidden signals in suspected carriers or at the least detect which media contain hidden signals. Therefore, an important consideration in steganography is how robust to detection is a particular technique. We review the existing steganography and steganalysis techniques and discuss their limitations and some possible research directions. Key words: Information hiding, steganography, steganalysis, watermarking 1

Perfectly Secure Steganography: Capacity, Error Exponents, and Code Constructions

IEEE Transactions on Information Theory, 2000

An analysis of steganographic systems subject to the following perfect undetectability condition is presented in this paper. Following embedding of the message into the covertext, the resulting stegotext is required to have exactly the same probability distribution as the covertext. Then no statistical test can reliably detect the presence of the hidden message. We refer to such steganographic schemes as perfectly secure. A few such schemes have been proposed in recent literature, but they have vanishing rate. We prove that communication performance can potentially be vastly improved; specifically, our basic setup assumes independently and identically distributed (i.i.d.) covertext, and we construct perfectly secure steganographic codes from public watermarking codes using binning methods and randomized permutations of the code. The permutation is a secret key shared between encoder and decoder. We derive (positive) capacity and random-coding exponents for perfectly-secure steganographic systems. The error exponents provide estimates of the code length required to achieve a target low error probability.

An Information-Theoretic Model for Steganography * Christian Cachin

An information-theoretic model for steganography with a passive adversary is proposed. The adversary's task of distinguishing between an innocent cover message C and a modified message S containing hidden information is interpreted as a hypothesis testing problem. The security of a steganographic system is quantified in terms of the relative entropy (or discrimination) between the distributions of C and S, which yields bounds on the detection capability of any adversary. It is shown that secure steganographic schemes exist in this model provided the covertext distribution satisfies certain conditions. A universal stegosystem is presented in this model that needs no knowledge of the covertext distribution, except that it is generated from independently repeated experiments. * To appear in Information and Computation. A preliminary version of this work was presented at the 2nd

Hide and seek: An introduction to steganography

Security & Privacy, IEEE, 2003

Although people have hidden secrets in plain sightnow called steganography-throughout the ages, the recent growth in computational power and technology has propelled it to the forefront of today's security techniques.

Digital invisible ink and its applications in steganography

Proceeding of the 8th workshop on Multimedia and security - MM&Sec '06, 2006

A novel information-hiding methodology denoted as digital invisible ink is introduced. The proposed approach is inspired by the invisible ink in the real world and can be regarded as an extension of the informed-embedding methodology. Messages hidden in digital contents using digital invisible ink cannot be correctly or clearly revealed unless certain pre-negotiated manipulations have been applied to the marked work. To facilitate such behavior, models and implementations based on both spreadspectrum and quantization-based watermarking approaches are investigated. Finally, benefits and limitations for applying digital invisible ink in common steganography systems and secret communications enabling plausible deniability are discussed.

Perturbed quantization steganography

Multimedia Systems, 2005

In this paper, we use the recently proposed wet paper codes and introduce a new approach to passive-warden steganography called Perturbed Quantization. In Perturbed Quantization, the sender hides data while processing the cover object with an informationreducing operation that involves quantization, such as lossy compression, downsampling, or A/D conversion. The unquantized values of the processed cover object are considered as side information to confine the embedding changes to those unquantized elements whose values are close to the middle of quantization intervals. This choice of the selection channel calls for wet paper codes as they enable communication with nonshared selection channel. Heuristic is presented that indicates that the proposed method provides better steganographic security than current JPEG steganographic methods. This claim is further supported by blind steganalysis of a specific case of Perturbed Quantization for recompressed JPEG images.

Information-Theoretic Approach to Steganographic Systems

2007 IEEE International Symposium on Information Theory, 2007

We propose a simple universal (that is, distributionfree) steganographic system in which covertexts with and without hidden texts are statistically indistinguishable. The stegosystem can be applied to any source generating i.i.d. covertexts with unknown distribution, and the hidden text is transmitted exactly, with zero probability of error. Sequences of covertexts with and without hidden information obey the same distribution (the stegosystem is perfectly secure). The proposed steganographic system has two important properties. First, the rate of transmission of hidden information approaches the Shannon entropy of the covertext source as the size of blocks used for hidden text encoding tends to infinity. Second, if the size of the alphabet of the covertext source and its minentropy tend to infinity then the number of bits of hidden text per letter of covertext tends to log(n!)/n where n is the (fixed) size of blocks used for hidden text encoding. Besides, the resource complexity of the proposed algorithms grows only polynomially.