Areeba Fatima

Optical image encryption using equal modulus decomposition and multiple diffractive imaging

The equal modulus decomposition (EMD) is a novel asymmetric cryptosystem based on coherent superposition which was proposed to resist the specific attack. In a subsequent work, the scheme was shown to be vulnerable to specific attack. In this paper, we counter the vulnerability through an encoding technique which uses multiple diffraction intensity pattern recordings as the input to the EMD setup in the gyrator domain. This allows suppression of the random phase mask in the EMD path. As a result, the proposed scheme achieves resistance to specific attack. The simulation results and the security analysis demonstrate that EMD based on multiple intensity pattern recording is an effective optical asymmetric cryptosystem suitable for securing data and images.

Discussion on comparative analysis and a new attack on optical asymmetric cryptosystem

This paper presents two different aspects of cryptanalysis of the optical phase-truncated Fourier transform (PTFT)-based cryptosystem. In the first part, a comparative study is carried out for a specific attack on the PTFT-based scheme in different optical transformation domains. In the second part, a new attack algorithm is proposed. The existing attack algorithms devised for the PTFT-based cryptosystem require knowledge of both the encryption keys for successful retrieval of phase through phase-retrieval algorithms to extract information about the plaintext. The proposed new attack method eliminates the requirement of one of the encryption keys to carry out the attack on the PTFT-based scheme. The numerical results support the proposed method.

Image authentication using a vector beam with sparse phase information

We propose a novel optical information authentication scheme that uses Stokes polarimetry of vector beams. Phase-only functions of the plaintext are generated using a modified Gerchberg-Saxton algorithm. Partial information of these phase functions is used to tailor the phase of a vector beam. The Stokes parameters recording of the vector beam generates the ciphertext, which contains sparse information of the input image. In contrast to most authentication schemes, the proposed scheme can authenticate two images from a single real ciphertext. Computer simulation results prove the feasibility of the proposed scheme.

Simultaneous authentication verification of multiple secured images using joint transform correlation approach

Optical techniques have been widely studied for securing and validating information, which is one of the most important challenges of the present time. In this work, we study simultaneous authentication of multiple input encrypted images which have been multiplexed in a single plane. The interference-based encryption architecture is used to generate two phase masks for each distinct image, which would serve as the phase lock and the phase key. The phases are made sparse by randomly retaining few pixels of the phase values. The phase locks corresponding to different images are then multiplexed in a single plane. For authenticating the phase masks, the concept of nonlinear correlation has been applied, which offer better correlation peaks than the conventional joint transform correlators. The proposed idea aims to achieve simultaneous encryption and authentication of multiple images and overcomes the constraints of storage issue.

Single Public Key Dependent Attack on Optical Asymmetric Cryptosystem

This work aims to study the vulnerability of the phase-truncated Fourier transform (PTFT) based cryptosystem towards single key attack analysis. The existing attack algorithms aimed at retrieving the input information from the PTFT cryptosystems require the knowledge of both the encryption keys. In this work, we aim to retrieve the plaintext through phase retrieval algorithm that uses only one of the keys as its constraints. The proposed method is supported by simulation results.

Gyrator wavelet transform

The gyrator transform is a linear canonical transform, which generates the rotation of an optical signal in position-spatial frequency planes. Gyrator wavelet transform is a relatively newer optical information processing tool obtained by combining the gyrator transform with the wavelet transform. This combination provides multi-resolution analysis of an image which is twisted in spatial frequency planes. The proposed tool satisfies basic algebraic properties, such as the linearity property and Parsevals theorem. Considering the usefulness of this tool, here a study of features, applications, and implementation of the gyrator wavelet transform is presented. This work studies the features of the gyrator wavelet transform, which can find a role in different applications such as edge enhancement, image encryption, image hiding, and watermarking.

Plasmonics-based Keys for Optical Image Encryption

We have generated the encryption keys from a nanosphere using gyrator transform. Through these keys, an input image has been encrypted using double random amplitude encoding scheme. As a proof-of-concept the simulation results have been presented.