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1

Asymmetric cryptosystem with random decomposition using fractional Fourier and Fourier transforms

Gaur Kapil Shankar, Singh Hukum, Thakran Seema

Optica Applicata

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2023

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Vol. 53, nr 4

591--602

EN

In this paper, an asymmetric cryptosystem based on random decomposition is proposed. The suggested scheme used three different decryption keys to get decrypted image, two of which are generated using phase truncation and one through random decomposition. The combination of these keys and fractional Fourier transform parameter increase the security of cryptosystem against various attacks. MATLAB simulations are used to validate the scheme’s conclusions. The effectiveness of a scheme is validated by the key sensitivity performance of the cryptosystem. This research also includes a 3D plot for both grayscale and binary images. Correlation coefficient (CC) values between the original and recovered images is also calculated to validate the cryptosystem.

2

Image encryption algorithm based on rear-mounted phase mask and random decomposition

Yadav Shivani, Singh Hukum

Optica Applicata

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2022

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Vol. 52, nr 2

195--212

EN

To escalate the image encryption a new method has been devised which includes double random phase encoding (DRPE) using rear phase masking and random decomposition (RD) technique stranded on fractional Fourier transform. Here, asymmetric cryptographic system is developed in fractional Fourier transform (FrFT) mode using two random phase masks (RPM) and a rear mounted phase mask. In the projected scheme a colored image is decomposed into R, G and B channels. The amplitude of each channel is normalized, phase encoded and modulated using RPM. The modulated R, G and B channels of the colored image are individually transformed using FrFT to produce corresponding encrypted image. The proposed scheme is authorized on grayscale image also. The norm behind the development of the suggested scheme has been elaborated by carrying out cryptanalysis on system based on the RD. The method helps in escalations of the protection of double random phase encoding by cumulating the key length and the parameter amount, so that it vigorously can be used against various attacks. The forte of the suggested cryptographic system was verified using simulations with MATLAB 7.9.0 (R2008a). The efficiency of the suggested scheme includes the analysis using singular value decomposition (SVD), histogram and correlation coefficient.

3

Audio and image encryption scheme based on QR decomposition and random modulus decomposition in Fresnel domain

Anjana Savita, Yadav Ak, Singh Phool, Singh Hukum

Optica Applicata

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2022

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Vol. 52, nr 3

359--374

EN

In this paper, an asymmetric audio and image encryption mechanism using QR decomposition and random modulus decomposition (RD) in the Fresnel domain is proposed. The audio file is recorded as a vector and converted to a two-dimensional array to act as an image or a sound map. This sound map is encrypted using the image encryption algorithm proposed in this paper. The proposed cryptosystem is validated for both audios and grayscale images. Fresnel parameters and the two private keys obtained from QR decomposition and random modulus decomposition (RD) form the key space. Computer-based reproductions have been carried out to prove the validity and authenticity of the scheme. Simulation results authenticate that the scheme is robust and efficient against various attacks and is sensitive to input parameters.

4

Asymmetric double image encryption, compression and watermarking scheme based on orthogonal-triangular decomposition with column pivoting

Anjana Savita, Rakheja Pankaj, Yadav Ak, Singh Phool, Singh Hukum

Optica Applicata

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2022

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Vol. 52, nr 2

283--295

EN

A novel asymmetric scheme for double image encryption, compression and watermarking based on QR decomposition in the Fresnel domain has been presented. The QR decomposition provides a permutation matrix as a ciphertext, and the product of orthogonal and triangular matrix as a key. The ciphertext obtained through this process is a sparse matrix that is compressed by the CSR method to give compressed encrypted data, which when combined with a host image, gives a watermarked image. Thus, a cryptosystem that involves compression and watermarking is proposed. The proposed scheme is validated for grayscale images. To check the efficacy of the proposed scheme, histograms, statistical parameters, and key sensitivity are analyzed. The scheme is also tested against various attacks. Numerical simulations are performed to validate the security of the scheme.