Optical Asymmetric Cryptography Modifying the RSA Public-key Protocol

전석희,길상근 한국광학회 2020 Current Optics and Photonics Vol.4 No.2

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 publickey-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.

위상천이 디지털 간섭계를 이용한 암호화된 지문 정합 필터기반의 인증 기법

전석희,길상근 한국전기전자학회 2023 전기전자학회논문지 Vol.27 No.2

본 논문은 디지털 간섭계를 이용한 정합 필터 기반의 새로운 인증 기법을 제안한다. 제안한 인증 시스템에서 광학적 위상 천이간섭계 기법을 적용하여 QR code로 변환된 사용자들의 개인 정보를 사용자 지문 개인키로 암호화함으로써 복소 홀로그램 형태의정합 필터를 구성한다. 사용자의 인증은 사용자의 지문 개인키를 통한 사용자의 QR code를 복호화하고 확인함으로써 이루어진다. 제안한 방법은 자기 상관 출력 평균제곱오차(MSE)가 약 5.55%로 상호 상관 MSE 76.17%보다 약 13.7배 적게 나와 인증에 타당함을 확인하였고, 데이터 베이스에서 개인 지문의 정보가 암호화 형태로 저장되므로 기존의 인증 방법에서의 지문 정보 해킹에 대하여강한 인증시스템을 제공할 수 있다.

Secret Key Sharing Cryptosystem using Optical Phase-shifting Digital Holography

전석희,길상근 한국광학회 2019 Current Optics and Photonics Vol.3 No.2

A new secret-key-sharing cryptosystem using optical phase-shifting digital holography is proposed. The proposed secret-key-sharing algorithm is based on the Diffie-Hellman key-exchange protocol, which is modified to an optical cipher system implemented by a two-step quadrature phase-shifting digital holographic encryption method using orthogonal polarization. Two unknown users’ private keys are encrypted by two-step phase-shifting digital holography and are changed into three digital-hologram ciphers, which are stored by computer and are opened to a public communication network for secret-key-sharing. Two-step phase-shifting digital holograms are acquired by applying a phase step of 0 or π/2 in the reference beam’s path. The encrypted digital hologram in the optical setup is a Fourier-transform hologram, and is recorded on CCDs with 256 quantized gray-level intensities. The digital hologram shows an analog-type noise-like randomized cipher with a two-dimensional array, which has a stronger security level than conventional electronic cryptography, due to the complexity of optical encryption, and protects against the possibility of a replay attack. Decryption with three encrypted digital holograms generates the same shared secret key for each user. Schematically, the proposed optical configuration has the advantage of producing a kind of double-key encryption, which can enhance security strength compared to the conventional Diffie-Hellman key-exchange protocol. Another advantage of the proposed secret-key-sharing cryptosystem is that it is free to change each user’s private key in generating the public keys at any time. The proposed method is very effective cryptography when applied to a secret-key-exchange cryptosystem with high security strength.

Optical Secret Key Sharing Method Based on Diffie-Hellman Key Exchange Algorithm

전석희,길상근 한국광학회 2014 Current Optics and Photonics Vol.18 No.5

In this paper, we propose a new optical secret key sharing method based on the Diffie-Hellman key exchange protocol required in cipher system. The proposed method is optically implemented by using a free-space interconnected optical logic gate technique in order to process XOR logic operations in parallel. Also, we present a compact type of optical module which can perform the modified Diffie-Hellman key exchange for a cryptographic system. Schematically, the proposed optical configuration has an advantage of producing an open public key and a shared secret key simultaneously. Another advantage is that our proposed key exchange system uses a similarity to double key encryption techniques to enhance security strength. This can provide a higher security cryptosystem than the conventional Diffie-Hellman key exchange protocol due to the complexity of the shared secret key. Results of numerical simulation are presented to verify the proposed method and show the effectiveness in the modified Diffie-Hellman key exchange system.

Simulated Annealing 알고리즘을 이용한 공간 코딩 BPOF 특성에 관한 연구 ( A Study on the Space-coded BPOF Characteristics using a Simulated Annealing Algorithm )

전석희,김창기,정창규,박한규 한국통신학회 1992 한국통신학회 학술대회 및 강연회 Vol.1992 No.-

Proposal for Optical One-time Password Authentication Using Digital Holography

전석희,길상근 한국광학회 2016 Current Optics and Photonics Vol.20 No.6

A new optical one-time password (OTP) authentication method using digital holography is proposed,which enhances security strength in the authentication system. A challenge-response optical OTP algorithmbased on two-factor authentication is presented using two-step phase-shifting digital holography, andtwo-way authentication is also performed using challenge-response handshake in both directions. Identification(ID), password (PW), and OTP are encrypted with a shared key by applying phase-shifting digital holography,and these encrypted pieces of information are verified by each party by means of the shared key. Theencrypted digital holograms are obtained by Fourier-transform holography and are recorded on a CCDwith 256 quantized gray-level intensities. Because the intensity pattern of such an encrypted digitalhologram is distributed randomly, it guards against a replay attack and results in higher security level. The proposed method has advantages, in that it does not require a time-synchronized OTP, and can beapplied to various authentication applications. Computer experiments show that the proposed method isfeasible for high-security OTP authentication.

Dual Optical Encryption for Binary Data and Secret Key Using Phase-shifting Digital Holography

전석희,길상근 한국광학회 2012 Current Optics and Photonics Vol.16 No.3

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 π/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.

Optical Implementation of Asymmetric Cryptosystem Combined with D-H Secret Key Sharing and Triple DES

전석희,길상근 한국광학회 2015 Current Optics and Photonics Vol.19 No.6

In this paper, an optical implementation of a novel asymmetrical cryptosystem combined with D-H secretkey sharing and triple DES is proposed. The proposed optical cryptosystem is realized by performingfree-space interconnected optical logic operations such as AND, OR and XOR which are implementedin Mach-Zehnder type interferometer architecture. The advantage of the proposed optical architectureprovides dual outputs simultaneously, and the encryption optical setup can be used as decryption opticalsetup only by changing the inputs of SLMs. The proposed cryptosystem can provide higher security strengththan the conventional electronic algorithm, because the proposed method uses 2-D array data, which canincrease 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’stwo private random numbers in generating the public keys at any time. Numerical simulation andperformance analysis verify that the proposed asymmetric cryptosystem is effective and robust againstattacks for the asymmetrical cipher system

Optical Implementation of Triple DES Algorithm Based on Dual XOR Logic Operations

전석희,길상근 한국광학회 2013 Current Optics and Photonics Vol.17 No.5

In this paper, we propose a novel optical implementation of a 3DES algorithm based on dual XOR logic operations for a cryptographic system. In the schematic architecture, the optical 3DES system consists of dual XOR logic operations, where XOR logic operation is implemented by using a free-space interconnected optical logic gate method. The main point in the proposed 3DES method is to make a higher secure cryptosystem, which is acquired by encrypting an individual private key separately, and this encrypted private key is used to decrypt the plain text from the cipher text. Schematically, the proposed optical configuration of this cryptosystem can be used for the decryption process as well. The major advantage of this optical method is that vast 2-D data can be processed in parallel very quickly regardless of data size. The proposed scheme can be applied to watermark authentication and can also be applied to the OTP encryption if every different private key is created and used for encryption only once. When a security key has data of 512×256 pixels in size, our proposed method performs 2,048 DES blocks or 1,024 3DES blocks cipher in this paper. Besides, because the key length is equal to 512×256 bits, 2512×256attempts are required to find the correct key. Numerical simulations show the results to be carried out encryption and decryption successfully with the proposed 3DES algorithm.

2-step Phase-shifting Digital Holographic Optical Encryption and Error Analysis

전석희,길상근 한국광학회 2011 Current Optics and Photonics Vol.15 No.3

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 π/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.