Discrete Cosine Transformation Based Image Authentication and Secret Message Transmission Scheme

Abstract: This paper proposes a novel image authentication scheme in the wavelet domain. The scheme uses a semi-fragile watermark to detect and precisely locate malicious tampering in images. The wavelet coefficients selected for embedding are randomly permuted with a secret key, achieving high security. A bit of the watermark is embedded in a group of coefficients by means of quantization. The experimental results show, that our algorithm achieves high image quality and high tampering detection resolution at a low watermark payload, compared to block-based authentication schemes. Thanks to the random permutation, the watermark is protected against local attacks. We have also conducted experiments to demonstrate the robustness of the watermark against mild to moderate JPEG compression.

Abstract: This paper deals with a watermarking scheme for images captured by mobile phone cameras. The new scheme embeds two watermarks in the images for authentication checking and copyright protection. The mobile phone number including the international code is used as the first robust watermark. The number is embedded using the discrete wavelet transform. Hash code of the image is used as a fragile watermark and inserted in the spatial domain. The scheme is blind and does not require the original image in order to extract the watermarks. The fragile watermark is very sensitive to any kind of attacks or image manipulations. On the other hand, the robust watermark causes minimal distortion to the host images. The robustness of the proposed algorithm has been tested against several attacks and it survived cropping, scaling, filtering, additive noise and JPEG compression.

Abstract: An improved method for embedding a secret message into a cover image with least significant bit (LSB) substitution in discrete cosine transformation (DCT) domain was proposed. The secret message was first split into partitions, while the cover image was divided into blocks of size 2x2, and DCT was used to convert the blocks from spatial domain to frequency domain. Then, Particle Swarm Optimization (PSO) algorithm was applied to search for an optimal substitution matrix T to transform the split partitions for an optimal embedding. Next, the transformed part of secret message was embedded into the AC coefficients of the transformed image blocks by LSB substitution. Experimental results show the proposed method can keep the quality of the stego-image better, while the security of the hidden secret message is increased by use of the substitution matrix T.

Abstract: The demand for effective information security schemes is increasing day by day, with the exponential growth and use of Internet. Cryptography and Steganography are two popular techniques, which are to be used for effective secret communications. . In this paper I have proposed a scheme, which can encode a text message and transmit it safely to its destination. Moreover the receiver can authenticate the received message to ensure that any intruder has not altered the original message. To facilitate the authentication facility, a hash code will be generated by the original message, which will be sent to the receiver securely. The hash code will be sent to receiver by hiding it into an image using image steganography. The receiver will decrypt the cipher text message to get the plaintext message. After that receiver will calculate the hash code with the received message and will compare this, with the received hash code. If both the hash codes are equal, it means that the received message is the original message. For generating the hash code, I have used SHA-1 method, and also analysed its performance and compared with that of MD5 method. KeywordsSteganography, Authentication, Hash

Abstract: This paper proposes a steganography technique to enhance the capacity and quality of the stego object. The method is proposed for frequency domain grayscale images. It is assumed that hiding varied number of secret bits in the original image blocks depending upon the DCT coefficients remaining after quantizing the blocks might increase the capacity of the stego image. To enhance the quality PSO can be used to find the appropriate DCT coefficients to conceal the secret data. The secret message is to be encrypted using AES before embedding in the original image blocks to ensure security.

Abstract: We consider the problem of embedding one signal (e.g., a digital watermark), within another "host" signal to form a third, "composite" signal. The embedding is designed to achieve efficient tradeoffs among the three conflicting goals of maximizing the information-embedding rate, minimizing the distortion between the host signal and composite signal, and maximizing the robustness of the embedding. We introduce new classes of embedding methods, termed quantization index modulation (QIM) and distortion-compensated QIM (DC-QIM), and develop convenient realizations in the form of what we refer to as dither modulation. Using deterministic models to evaluate digital watermarking methods, we show that QIM is "provably good" against arbitrary bounded and fully informed attacks, which arise in several copyright applications, and in particular it achieves provably better rate distortion-robustness tradeoffs than currently popular spread-spectrum and low-bit(s) modulation methods. Furthermore, we show that for some important classes of probabilistic models, DC-QIM is optimal (capacity-achieving) and regular QIM is near-optimal. These include both additive white Gaussian noise (AWGN) channels, which may be good models for hybrid transmission applications such as digital audio broadcasting, and mean-square-error-constrained attack channels that model private-key watermarking applications.

Abstract: An information-theoretic analysis of information hiding is presented, forming the theoretical basis for design of information-hiding systems. Information hiding is an emerging research area which encompasses applications such as copyright protection for digital media, watermarking, fingerprinting, steganography, and data embedding. In these applications, information is hidden within a host data set and is to be reliably communicated to a receiver. The host data set is intentionally corrupted, but in a covert way, designed to be imperceptible to a casual analysis. Next, an attacker may seek to destroy this hidden information, and for this purpose, introduce additional distortion to the data set. Side information (in the form of cryptographic keys and/or information about the host signal) may be available to the information hider and to the decoder. We formalize these notions and evaluate the hiding capacity, which upper-bounds the rates of reliable transmission and quantifies the fundamental tradeoff between three quantities: the achievable information-hiding rates and the allowed distortion levels for the information hider and the attacker. The hiding capacity is the value of a game between the information hider and the attacker. The optimal attack strategy is the solution of a particular rate-distortion problem, and the optimal hiding strategy is the solution to a channel-coding problem. The hiding capacity is derived by extending the Gel'fand-Pinsker (1980) theory of communication with side information at the encoder. The extensions include the presence of distortion constraints, side information at the decoder, and unknown communication channel. Explicit formulas for capacity are given in several cases, including Bernoulli and Gaussian problems, as well as the important special case of small distortions. In some cases, including the last two above, the hiding capacity is the same whether or not the decoder knows the host data set. It is shown that many existing information-hiding systems in the literature operate far below capacity.

Abstract: There have been many techniques for hiding messages in images in such a manner that the alterations made to the image are perceptually indiscernible. However, the question whether they result in images that are statistically indistinguishable from untampered images has not been adequately explored. We look at some specific image based steganography techniques and show that an observer can indeed distinguish between images carrying a hidden message and images which do not carry a message. We derive a closed form expression of the probability of detection and false alarm in terms of the number of bits that are hidden. This leads us to the notion of steganographic capacity, that is, how many bits can we hide in a message without causing statistically significant modifications? Our results are able to provide an upper bound on the this capacity. Our ongoing work relates to adaptive steganographic techniques that take explicit steps to foil the detection mechanisms. In this case we hope to show that the number of bits that can be embedded increases significantly.

Abstract: This paper introduces a new, principled approach to detecting least significant bit (LSB) steganography in digital signals such as images and audio. It is shown that the length of hidden messages embedded in the least significant bits of signal samples can be estimated with relatively high precision. The new steganalytic approach is based on some statistical measures of sample pairs that are highly sensitive to LSB embedding operations. The resulting detection algorithm is simple and fast. To evaluate the robustness of the proposed steganalytic approach, bounds on estimation errors are developed. Furthermore, the vulnerability of the new approach to possible attacks is also assessed, and counter measures are suggested.

Abstract: This paper introduces a new, principled approach to detecting LSB steganography in digital signals such as images and audio. It is shown that the length of hidden message embedded in the least significant bits of signal samples can be estimated with relatively high precision. The new steganalytic approach is based on some statistical measures of sample pairs that are highly sensitive to LSB embedding operations. The resulting detection algorithm is simple and fast. To evaluate the robustness of the proposed steganalytic approach, bounds on estimation errors are developed. Furthermore, the vulnerability of the new approach to possible attacks is also assessed, and counter measures are suggested.