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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

2022

Vol. 52, nr 2

283--295

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.

Digital holography and holographic interferometry

Kreis T. M.

Machine Graphics and Vision

1999

Vol. 8, No. 4

611-624

Holography is a method for three-dimensional imaging frequently used in metrology and nondestructive testing. Up to now both the generation of the holograms as well as the reconstruction of the wavefields was performed optically. In digital holography optically generated Fresnel- or Fraunhofer holograms are recorded by a CCD array. The reconstruction of the wavefields is done digitally by image processing methods based on the mathematical concept of the diffraction integral. Two approaches to its numerical solution are the finite discrete Fresnel transform and a procedure employing the convolution theorem. Both approaches result in a complex field from which intensity and phase can be determined. In digital holographic interferometry the sign-correct interference phase distribution is computed with high accurancy by subtraction of two numerically reconstructed phase distributions.