• Current Optics and Photonics
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• v.2 no.4
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• pp.368-377
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• 2018

In this paper, we evaluate cryptographic properties of a double random phase encoding (DRPE) scheme in the discrete Gyrator domain with avalanche and bit independence criterions. DRPE in the discrete Gyrator domain is reported to have higher security than traditional DRPE in the Fourier domain because the rotation angle involved in the Gyrator transform is viewed as additional secret keys. However, our numerical experimental results demonstrate that the DRPE in the discrete Gyrator domain has an excellent bit independence feature but does not possess a good avalanche effect property and hence needs to be improved to satisfy with acceptable avalanche effect that would be robust against statistical-based cryptanalysis. We compare our results with the avalanche and bit independence criterion (BIC) performances of the conventional DRPE scheme, and improve the avalanche effect of DRPE in the discrete Gyrator domain by integrating a photon counting imaging technique. Although the Gyrator transform-based image cryptosystem has been studied, to the best of our knowledge, this is the first report on a cryptographic evaluation of discrete Gyrator transform with avalanche and bit independence criterions.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.42-54
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• 2016

A hybrid color and grayscale images encryption scheme based on the quaternion Hartley transform (QHT), the two-dimensional (2D) logistic map, the double random phase encoding (DRPE) in gyrator transform (GT) domain and the three-step phase-shifting interferometry (PSI) is presented. First, we propose a new color image processing tool termed as the quaternion Hartley transform, and we develop an efficient method to calculate the QHT of a quaternion matrix. In the presented encryption scheme, the original color and grayscale images are represented by quaternion algebra and processed holistically in a vector manner using QHT. To enhance the security level, a 2D logistic map-based scrambling technique is designed to permute the complex amplitude, which is formed by the components of the QHT-transformed original images. Subsequently, the scrambled data is encoded by the GT-based DRPE system. For the convenience of storage and transmission, the resulting encrypted signal is recorded as the real-valued interferograms using three-step PSI. The parameters of the scrambling method, the GT orders and the two random phase masks form the keys for decryption of the secret images. Simulation results demonstrate that the proposed scheme has high security level and certain robustness against data loss, noise disturbance and some attacks such as chosen plaintext attack.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.4
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• pp.23-30
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• 1980

All the resistors in the active RC filter networks cab be replaced by the switched capaciters, The swiftched capacitor is much bet tar than a resistor in temperature and linearity characteristics, and the former can be fabricated on the much smaller silicon area than the latter. In this paper, it is given the generaliged design method of the active SC filter from the active RC filter using Bilinear Z-transformatirm. SC filtering techniques using Bilinear Z-transform enable us to realize the FDNR and Gyrator filters which could not be realized by the exsisting designs 1 and to utilize the processing of signals at much higher frequencies than the conventional design method. Experiments show that the response of the active SC filter is similiar to that of its prototype active RC filler.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.4 no.1
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• pp.25-31
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• 1979

All the resitors in the active RC filter networks can be relplaced by the switched capacitors. Therefore, An SC filter circuit can be fully integrated using MOS technology. A switched capacitor is much better than a resistor in temperature and linearity characteristics, and the former can be fabricated on the much smaller area then the latter. In this paper, It is given the generalized disign method of the active SC filter from the active RC filter using Bilinear Z-transformation. By SC filtering Techniques using Bilinear Z-transform, It enalbes us to realize the FDNR and Gyrator filters, which could not be realized in the exsisting designs, and it permits the processing of signals at much higher frequenies that many previous designs do. Experiments show that the response of the SC active filter is similiar to that of its prototype active RC filter.