• Journal of the Optical Society of Korea
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• 제6권4호
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• pp.156-160
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• 2002

In this paper, we propose an improved optical security system using three phase-encoded images and the principle of interference. This optical system based on a Mach-Zehnder interferometer consists of one phase-encoded virtual image to be encrypted and two phase-encoded images, en-crypting image and decrypting image, where every pixel in the three images has a phase value of '0'and'$\pi$'. The proposed encryption is performed by the multiplication of an encrypting image and a phase-encoded virtual image which dose not contain any information from the decrypted im-age. Therefore, even if the unauthorized users steal and analyze the encrypted image, they cannot reconstruct the required image. This virtual image protects the original image from counterfeiting and unauthorized access. The decryption of the original image is simply performed by interfering between a reference wave and a direct pixel-to-pixel mapping image of the en crypted image with a decrypting image. Computer simulations confirmed the effectiveness of the proposed optical technique for optical security applications.

• Current Optics and Photonics
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• 제4권2호
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• pp.103-114
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• 2020

A new optical asymmetric cryptosystem is proposed by modifying the asymmetric RSA public-key protocol required in a cryptosystem. The proposed asymmetric public-key algorithm can be optically implemented by combining a two-step quadrature phase-shifting digital holographic encryption method with the modified RSA public-key algorithm; then two pairs of public-private keys are used to encrypt and decrypt the plaintext. Public keys and ciphertexts are digital holograms that are Fourier-transform holograms, and are recorded on CCDs with 256-gray-level quantized intensities in the optical architecture. The plaintext can only be decrypted by the private keys, which are acquired by the corresponding asymmetric public-key-generation algorithm. Schematically, the proposed optical architecture has the advantage of producing a complicated, asymmetric public-key cryptosystem that can enhance security strength compared to the conventional electronic RSA public-key cryptosystem. Numerical simulations are carried out to demonstrate the validity and effectiveness of the proposed method, by evaluating decryption performance and analysis. The proposed method shows feasibility for application to an asymmetric public-key cryptosystem.

• Current Optics and Photonics
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• 제7권6호
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• pp.673-682
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• 2023

In this paper, a three-key triple data encryption algorithm (TDEA) of a digital cryptosystem based on phase-shifting interferometry is proposed. The encryption for plaintext and the decryption for the ciphertext of a complex digital hologram are performed by three independent keys called a wavelength key k₁(λ), a reference distance key k₂(d_r) and a holographic encryption key k₃(x, y), which are represented in the reference beam path of phase-shifting interferometry. The results of numerical simulations show that the minimum wavelength spacing between the neighboring independent wavelength keys is about δλ = 0.007 nm, and the minimum distance between the neighboring reference distance keys is about δd_r = 50 nm. For the proposed three-key TDEA, choosing the deviation of the key k₁(λ) as δλ = 0.4 nm and the deviation of the key k₂(d_r) as δd_r = 500 nm allows the number of independent keys k₁(λ) and k₂(d_r) to be calculated as N(k₁) = 80 for a range of 1,530-1,562 nm and N(d_r) = 20,000 for a range of 35-45 mm, respectively. The proposed method provides the feasibility of independent keys with many degrees of freedom, and then these flexible independent keys can provide the cryptosystem with very high security.

• 한국광학회지
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• 제17권5호
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• pp.401-411
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• 2006

보안 시스템에서 2-단계 위상 천이 홀로그래피를 이용하여 이진 정보 광 암호화 기법을 제안하였다. 위상 천이 디지털 간섭계는 CCD 카메라를 이용하여 위상과 크기 정보를 기록할 수 있는 기법이다. 2-단계 위상 천이는 0과 ${\pi}/2$의 위상 천이 각을 갖도록 PZT 거울을 움직여서 구현하였다. 이진 정보와 암호키는 랜덤 코드와 랜덤 위상으로 표현하였고, 디지털 홀로그램은 푸리에변환 홀로그램으로 간섭무늬는 CCD를 이용하여 256 레벨의 양자화 된 광세기로 획득되었다. 데이터 복원 시 DC 성분 제거 방법을 사용하였다. 컴퓨터 모의실험을 통하여 데이터 복원과 양자화 과정에서의 양자화 레벨 변화량과 디지털 홀로그램 간섭무늬의 오차 픽셀수에 따른 오차 분석을 수행하였다. 이 결과를 이용하여 정보의 광학적 암호화에 적용이 가능함을 확인하였다.

• Journal of Communications and Networks
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• 제15권5호
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• pp.457-463
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• 2013

In recent days, cooperative diversity and communication security become important research issues for wireless communications. In this paper, to achieve low probability of interception (LPI) and high throughput in the cooperative single-carrier frequency division multiple access (SC-FDMA) system, a new physical layer transmission scheme is proposed, where a new encryption algorithm is applied and adaptive modulation is further considered based on channel state information (CSI). By doing so, neither relay node nor eavesdropper can intercept the information signals transmitted from user terminal (UT). Simulation results show above new physical layer transmission scheme brings in high transmission safety and secrecy rate. Furthermore, by applying adaptive modulation and coding (AMC) technique according to CSI, transmission throughput can be increased significantly. Additionally, low peak-to-average power ratio (PAPR) characteristic can still be remained due to the uniform distribution of random coefficients used for encryption algorithm.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.62-63
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• 2003

We propose an improved image encryption and the shift-tolerance method in the Fourier space using a virtual phase image. The encrypted image is obtained by the Fourier transform of the product of a phase-encoded virtual image, not an original image, and a random phase image. We demonstrate the robustness to noise, to data loss and shift of the encrypted image or the Fourier decryption key in the proposed technique.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.592-603
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• 2015

In this paper, an optical implementation of a novel asymmetrical cryptosystem combined with D-H secret key sharing and triple DES is proposed. The proposed optical cryptosystem is realized by performing free-space interconnected optical logic operations such as AND, OR and XOR which are implemented in Mach-Zehnder type interferometer architecture. The advantage of the proposed optical architecture provides dual outputs simultaneously, and the encryption optical setup can be used as decryption optical setup only by changing the inputs of SLMs. The proposed cryptosystem can provide higher security strength than the conventional electronic algorithm, because the proposed method uses 2-D array data, which can increase the key length surprisingly and uses 3DES algorithm, which protects against “meet in the middle” attacks. Another advantage of the proposed asymmetrical cryptosystem is that it is free to change the user’s two private random numbers in generating the public keys at any time. Numerical simulation and performance analysis verify that the proposed asymmetric cryptosystem is effective and robust against attacks for the asymmetrical cipher system.

• 대한전자공학회논문지SD
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• 제41권11호
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• pp.43-51
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• 2004

본 논문에서는 원 영상의 컴퓨터 생성 홀로그램(computer generated hologram; CGH) 패턴을 위상 변조한 후, 위상 부호화한 무작위 키 영상들의 프레넬 회절(Fresnel difftaction) 위상 패턴과 곱하여 암호화함으로써 외부 교란이나 절단에 강하고, 암호화 수준이 높은 광 암호화 방법을 제안하였다. 암호화시 원 영상의 이진 CGH패턴을 위상 변조한 후, 이를 위상 키 영상들의 프레넬 회절 공액 위상정보와 곱하며, 복호화시 암호화 영상에 위상 키 영상들의 프레넬 회절 위상 정보를 다시 곱한 후 푸리에 변화시켜 원 영상 정보를 얻는다. 암호화 영상은 CGH 패턴 특성을 가지므로, 절단이나 외부 잡음에 강하며 프레넬 회절 정보를 이용하여 암호화함으로 높은 암호화 수준을 가진다. 컴퓨터 모의 실험을 통해 제안한 방법의 타당성을 확인하였으며 절단과 잡음에 대한 영향을 분석하였고, 위상 변조 특성이 있는 LCD를 사용하여 광학적으로 구현하였다.

• 한국광학회지
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• 제19권3호
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• pp.237-241
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• 2008

전자 논리회로에서 이용되는 전자신호 암호화와 같은 방법으로, 반도체 광 증폭기 XOR논리 게이트를 이용한 전광 암호화 시스템을 제안하였다. 시스템의 변수를 최적화 하고 전체 디자인 과정을 빠르게 수행하기 위해 정상상태와(steady state) 과도상태에(dynamic) 대한 전산모사가 차례로 이루어졌다. 심각한 신호 왜곡이 없이 10 Gbps 속도에서 일반적인 반도체 광 증폭기의 연속적 연결을 통해 전광 신호에 대한 암호화와 해독이 수행될 수 있음을 전산모사와 실험에 의한 결과를 통해 보여주었다.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.247-248
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• 2009