• Journal of Information Processing Systems
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• 제10권2호
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• pp.215-222
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• 2014

In this paper, we discuss optical encryption and decryption considering wireless communication channels. In wireless communication systems, the wireless channel causes noise and fading effects of the transmitted information. Optical encryption technique such as double-random-phase encryption (DRPE) is used for encrypting transmitted data. When the encrypted data is transmitted, the information may be lost or distorted because there are a lot of factors such as channel noise, propagation fading, etc. Thus, using digital modulation and maximum likelihood (ML) detection, the noise and fading effects are mitigated, and the encrypted data is estimated well at the receiver. To the best of our knowledge, this is the first report that considers the wireless channel characteristics of the optical encryption technique.

• Current Optics and Photonics
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• 제3권6호
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• pp.548-554
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• 2019

A binary encoding method for grayscale images is proposed to address their unsatisfactory decryption results from joint transform correlator (JTC) encryption systems. The method converts the encryption and decryption of grayscale images into that of binary images, and effectively improves decrypted-image quality. In the simulation, we replaced unencoded grayscale images with their binary encoded counterparts in the JTC encryption and decryption processes, then adopted a median filter to suppress saturation noise while keeping other settings unchanged. Accordingly, decrypted-image quality was clearly enhanced as the correlation coefficient (CC) between a decrypted image and its original rose from 0.8237 to 0.9473 initially, and then further to 0.9937, following the above two steps respectively. Finally, optical experimental results confirmed that the proposed encryption system works correctly.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.335-336
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• 2006

We propose a method of encryption and decryption of binary data using 2-step phase-shifting digital interferometry. This technique reduces the number of interferograms in the phase-shifting interferometry. The binary data has been expressed with random code and random phase. We remove the dc-term of the phase-shifting digital interferogram to restore the original binary data. Simulation results shows that the proposed technique can be used for binary data encryption and decryption.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.244-251
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• 2011

We propose a new 2-step phase-shifting digital holographic optical encryption technique and analyze tolerance error for this cipher system. 2-step phase-shifting digital holograms are acquired by moving the PZT mirror with phase step of 0 or ${\pi}$/2 in the reference beam path of the Mach-Zehnder type interferometer. Digital hologram with the encrypted information is Fourier transform hologram and is recorded on CCD camera with 256 gray-level quantized intensities. The decryption performance of binary bit data and image data is analyzed by considering error factors. One of the most important errors is quantization error in detecting the digital hologram intensity on CCD. The more the number of quantization error pixels and the variation of gray-level increase, the more the number of error bits increases for decryption. Computer experiments show the results to be carried out encryption and decryption with the proposed method and the graph to analyze the tolerance of the quantization error in the system.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.955-963
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• 2008

In this paper, we propose an improved practical encryption and fault-tolerance decryption method using a non-negative value key and random function obtained with a white noise by using iterative phase wrapping method. A phase wrapping operating key, which is generated by the product of arbitrary random phase images and an original phase image. is zero-padded and Fourier transformed. Fourier operating key is then obtained by taking the real-valued data from this Fourier transformed image. Also the random phase wrapping operating key is made from these arbitrary random phase images and the same iterative phase wrapping method. We obtain a Fourier random operating key through the same method in the encryption process. For practical transmission of encryption and decryption keys via Internet, these keys should be intensity maps with non-negative values. The encryption key and the decryption key to meet this requirement are generated by the addition of the absolute of its minimum value to each of Fourier keys, respectively. The decryption based on 2-f setup with spatial filter is simply performed by the inverse Fourier transform of the multiplication between the encryption key and the decryption key and also can be used as a current spatial light modulator technology by phase encoding of the non-negative values. Computer simulations show the validity of the encryption method and the robust decryption system in the proposed technique.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.358-362
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• 2016

We present a new scheme for optical encryption of a binary image. In our method, the original binary data page is first divided into two identical pages. In each data page, the “on” and “off” pixels are represented by two discrete phases that are 90° apart. The first page corresponds to the phase conjugation of the second page, and vice versa. In addition, the wavefront of the two data pages is changed simultaneously from planar to spherical, for better encryption. The wavefront modification is represented by an extra phase shift, which is a function of position on the wavefront. In this way the two separate pages are both encrypted, and therefore the pages cannot be distinguished in a CCD. If the first page is used as an encrypted data page, then the second page is used as the decryption key, and vice versa. The decryption can be done by simply combining the two encrypted data pages. It is shown in our experiment that encryption and decryption can be fully accomplished in the optical domain.

• 한국광학회지
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• 제15권2호
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• pp.114-122
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• 2004

본 논문에서는 콘포칼 구조의 광학계를 이용하여 생체신호인 조상(nail bed)패턴을 추출하고 그를 암호키로 이용해 암호 키(key)의 고의적 양도나 부정사용을 방지해 높은 보안성을 갖는 광 암호화 및 복호화 방법을 제안한다. 또한 암호화된 영상은 생체정보를 포함하고 있기 때문에 영상정보의 진위여부를 개인의 인증(authentication)을 통해서 가려낼 수 있다.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.263-269
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• 2012

In this paper, we propose a new dual optical encryption method for binary data and secret key based on 2-step phase-shifting digital holography for a cryptographic system. Schematically, the proposed optical setup contains two Mach-Zehnder type interferometers. The inner interferometer is used for encrypting the secret key with the common key, while the outer interferometer is used for encrypting the binary data with the same secret key. 2-step phase-shifting digital holograms, which result in the encrypted data, are acquired by moving the PZT mirror with phase step of 0 or ${\pi}/2$ in the reference beam path of the Mach-Zehnder type interferometer. The digital hologram with the encrypted information is a Fourier transform hologram and is recorded on CCD with 256 gray level quantized intensities. Computer experiments show the results to be encryption and decryption carried out with the proposed method. The decryption of binary secret key image and data image is performed successfully.

• 한국광학회지
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• 제14권6호
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• pp.630-635
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• 2003

광을 이용하여 암호화를 하는 경우는 위조 및 복제의 방지를 위하여 세기성분보다는 위상성분을 이용하여 주로 암호화를 하고 있다. 그러나 위상정보를 검출할 수 있는 장비가 개발된다면 정보를 유출 당할 수 있는 위험이 있다. 이러한 위험을 줄이기 위해 본 논문에서는 가상 위상영상을 이용하고 또한 정보를 다수가 공유할 수 있도록 시각 암호화(visual cryptography) 방법을 이용하여 정보를 보다 안전하게 보관하고 공유하는 시스템을 제안하였다.

• 전기전자학회논문지
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• 제18권3호
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• pp.328-334
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• 2014

본 논문은 OFB(Output Feedback Block) 블록 암호화 알고리즘에 대한 광학적 암호화 및 복호화 시스템을 제안한다. 제안한 방식은 암호화 과정에 필요한 XOR 논리 연산을 구현하기 위해 이중 인코딩 기법을 사용한다. 또한, 제안된 암호화 시스템은 광 병렬처리의 특성상 데이터가 2차원으로 배열되어 매우 큰 암호키를 구현할 수 있기 때문에 기존의 전자적 OFB 방식보다 한층 더 암호강도가 증강된 암호화 시스템을 제공한다. 마지막으로, 제안한 방식을 검증하기 위해 컴퓨터 시뮬레이션을 통하여 암호화 및 복호화 과정을 보여준다. 그 결과, 제안한 광학적 OFB 암호화 시스템은 광학적인 고속성과 병렬성의 이점까지 포함하기 때문에 더욱 효율적이고 강력한 광학적 블록 암호화 시스템이 가능하다.