Fawad Ahmed

A secure and robust hash-based scheme for image authentication

To authenticate an image using a hash function is a challenging task since several core issues like tamper detection, security and robustness needs to be addressed. In this paper, we propose a hash-based image authentication scheme that simultaneously attempts to address these core issues. Unlike most of the existing schemes that use secret key in the feature extraction stage, we use secret key to randomly modulate image pixels to create a transformed feature space. The key-dependent transformed feature space is then used to calculate the image hash. To reduce the size of the hash, a 4-bit quantization scheme is also proposed. The experimental results reported in this paper reveals that the proposed scheme offers good robustness against JPEG compression, low-pass and high-pass filtering. Besides being robust, the proposed hashing scheme can detect minute tampering with localization of the tampered area. These results along with the receiver operating curve (ROC) and security analysis presented in this work makes the proposed technique a candidate for practical digital image signature systems where the transmitted or stored image might undergo JPEG compression, low-pass or high-pass filtering.

A Perceptually Scalable and JPEG Compression Tolerant Image Encryption Scheme

In this paper, a perceptually scalable and JPEG compression tolerant DCT-based image encryption scheme is proposed. There are two main features of the proposed scheme, first the decryption algorithm is able to reconstruct the plaintext-image even if the encrypted image is JPEG compressed. Secondly, the encryption algorithm can be adjusted to produce cipher-image with varying perceptual distortion. The proposed encryption scheme relies on some very interesting properties of orthogonal matrices containing columns that form a set of orthonormal basis vectors. It is envisaged that the proposed cryptosystem would enable uncompressed encrypted image files to be transmitted or stored in the JPEG compressed domain thus saving bandwidth and or storage space. Further, the proposed scheme can be used either for low-level encryption in which the cipher-image has a degraded visual quality but reflects the contents of the plaintext-image, or high-level encryption in which the cipher-image does not reveal any information about the plaintext-image. Experimental results and security analysis is presented to show the viability of the proposed scheme.

A secure watermarking scheme for buyer-seller identification and copyright protection

We propose a secure watermarking scheme that integrates watermarking with cryptography for addressing some important issues in copyright protection. We address three copyright protection issues—buyer-seller identification, copyright infringement, and ownership verification. By buyer-seller identification, we mean that a successful watermark extraction at the buyers end will reveal the identities of the buyer and seller of the watermarked image. For copyright infringement, our proposed scheme enables the seller to identify the specific buyer from whom an illegal copy of the watermarked image has originated, and further prove this fact to a third party. For multiple ownership claims, our scheme enables a legal seller to claim his/her ownership in the court of law. We will show that the combination of cryptography with watermarking not only increases the security of the overall scheme, but it also enables to associate identities of buyer/seller with their respective watermarked images.

A secure and robust wavelet-based hashing scheme for image authentication

The purpose of an image hash is to provide a compact representation of the whole image. Designing a good image hash function requires careful consideration of many issues such as robustness, security and tamper detection with precise localization. In this paper, we present a novel hashing scheme that addresses these issues in a unified framework. We analyze the security issues in image hashing and present new ideas to counter some of the attacks that we shall describe in this paper. Our proposed scheme is resilient to allow non-malicious manipulations like JPEG compression, high pass filtering and is sensitive enough to detect tampering with precise localization. Several experimental results are presented to demonstrate the effectiveness of the proposed scheme.

A Secure and Robust Hashing Scheme for Image Authentication

An image hash function provides a condensed representation of an image that can be used for authentication purposes. Security, robustness and fragility are three important issues in designing a hashing scheme for image authentication. In this paper, we propose a secure image hashing scheme that allows acceptable manipulations like JPEG compression and low pass filtering and is sensitive enough in detecting malicious manipulations. To enforce security, we use key-dependent feature extraction to form the image hash. Several experimental results are presented to demonstrate the effectiveness of our proposed scheme

A novel approach for regenerating a private key using password, fingerprint and smart card

Purpose – To devise a biometric‐based mechanism for enhancing security of private keys used in cryptographic applications.Design/methodology/approach – To enhance security of a private key, we propose a scheme that regenerates a users private key by taking a genuine users password, fingerprint and a valid smart card. Our scheme uses features extracted from fingerprint along with public key cryptography, cryptographic hash functions and Shamir secret sharing scheme in a novel way to achieve our desired objectives.Findings – Despite changes in the fingerprint pattern each time it is presented, our scheme is sufficiently robust to regenerate a constant private key. As compared to conventional methods of storing a private key merely by password‐based encryption, our scheme offers more security as it requires a genuine users password, fingerprint and a valid smart card. Key lengths up to 1024‐bit or even higher can be regenerated making the scheme compatible with the current security requirements of public ...

A biometric-based scheme for enhancing security of cryptographic keys

In public key cryptography, the security of private keys is of vital importance. If a private key is ever compromised, it can be used to sign forge documents or to decrypt secret messages. Conventional methods such as password-based encryption that are used for safe custody of private keys do not provide adequate security due to very low entropy in user chosen passwords. In order to enhance the security of private keys, we propose a novel biometric-based method that dynamically regenerates the private key of a user rather than storing it directly in an encrypted form. Our proposed algorithm is capable of regenerating key lengths that can meet the current security requirements of any public key algorithm and is more secure than conventional methods of protecting private keys using password-based encryption.

A Secure and Robust DCT-Based Hashing Scheme for Image Authentication

The purpose of an image hash function is to provide a compact representation of an image that can be used for authentication purposes. Designing a good image hash function requires the consideration of many issues like robustness, security and tamper detection with precise localization. In this paper, we focus our attention towards DCT-based hashing schemes for image authentication. We first highlight the problems that we have discovered in some of the existing DCT-based hashing schemes proposed in the literature. We then propose solutions to counter these problems. We present experimental results to show the effectiveness of our proposed scheme. Although we focus on DCT-based hashing techniques, however, the type of problems highlighted in this paper may be present in other spatial or transform domain image hashing techniques as well

A Novel Hashing Scheme for Image Authentication

An image hash provides a compact representation of an image that can be used for authenticating that image. Designing a good image hashing technique requires many issues to be addressed such as robustness, security and tamper detection with precise localization. In this paper, we propose a novel image hashing scheme that addresses these issues in a unified framework. We extract features in the DCT domain to generate the image hash. To enforce security, we propose a new method that directly modulates pixels in the spatial domain based on a secret key. Our scheme is moderately robust against JPEG compression and fragile to detect and localize tampered areas in an image. Several experimental results are presented to demonstrate the effectiveness of the proposed scheme

A robust image encryption scheme using state-feedback control

In recent years, the security of multimedia data transmitted over insecure networks like the Internet has gained a lot of attention. Applying standard cryptographic encryption and authentication algorithms to multimedia data is not feasible because multimedia data may undergo certain content preserving operations that although may change the data values but keep the semantic of the data intact. In this paper, we propose a robust encryption algorithm for digital images that not only provides confidentiality to the image being transmitted or stored, but it can also tolerate JPEG compression. The proposed algorithm is private key i.e. the encryption and decryption process requires the same key. This paper presents an interesting approach by adapting techniques from modern control theory to devise the proposed encryption and decryption algorithms. The results reported in this paper are extremely encouraging and reflects the point that how multi-disciplinary fields can be combined to solve complex problems.