• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.2254-2275
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• 2017

In this paper, we present an IND-CCA2 secure certificateless proxy re-encryption scheme in the random oracle model. A certificateless public key cryptography simplifies the certificate management in a traditional public key infrastructure and the built-in key escrow feature in an identity-based public key cryptography. Our scheme shares the merits of certificateless public key encryption cryptosystems and proxy re-encryption cryptosystems. Our certificateless proxy re-encryption scheme has several practical and useful properties - namely, multi-use, unidirectionality, non-interactivity, non-transitivity and so on. The security of our scheme bases on the standard bilinear Diffie-Hellman and the decisional Bilinear Diffie-Hellman assumptions.

• 한국멀티미디어학회논문지
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• 제11권6호
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• pp.852-859
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• 2008

In this paper, we propose a dynamic keyed block encryption algorithm. Most existing encryption algorithms are designed such that the key is not changed. Therefore, they have a disadvantage that plaintext could be easily exposed by differential and linear cryptanalysis. In the proposed algorithm, several key generators are designed, and a key generator is attached to the encryption procedure. After performing the encryption procedure, ciphertext and the initial key generating values are transferred to the receiver's key generator for decryption. Through simulation, the proposed algorithm is verified to satisfy the requirements of real-time processing and proved to have a high strength. It can be applied to practical use.

• Current Optics and Photonics
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• 제3권4호
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• pp.320-328
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• 2019

A method for joint-transform correlator (JTC) multiple-image encryption based on a quick-response (QR) code key is proposed. The QR codes converted from different texts are used as key masks to encrypt and decrypt multiple images. Not only can Chinese text and English text be used as key text, but also symbols can be used. With this method, users have no need to transmit the whole key mask; they only need to transmit the text that is used to generate the key. The correlation coefficient is introduced to evaluate the decryption performance of our proposed cryptosystem, and we explore the sensitivity of the key mask and the capability for multiple-image encryption. Robustness analysis is also conducted in this paper. Computer simulations and experimental results verify the correctness of this method.

• Current Optics and Photonics
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• 제2권6호
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• pp.540-546
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• 2018

We propose an implementation scheme for an optical encryption system with hybrid-pattern random keys. In the encryption process, a pair of random phase keys composed of a white-noise phase key and a structured phase key are positioned in the input plane and Fourier-spectrum plane respectively. The output image is recoverable by digital reconstruction, using the conjugate of the encryption key in the Fourier-spectrum plane. We discuss the system encryption performance when different combinations of phase-key pairs are used. To measure the effectiveness of the proposed method, we calculate the statistical indicators between original and encrypted images. The results are compared to those generated from a classical double random phase encoding. Computer simulations are presented to show the validity of the method.

• 정보보호학회논문지
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• 제23권2호
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• pp.147-155
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• 2013

프록시 재암호화 기법은 데이터를 재암호화 하는 과정에서 평문이 노출되지 않는 장점이 있다. 이 기법은 최근 클라우드 컴퓨팅, 모바일 오피스 등 서버를 이용하는 환경에서 저장된 데이터를 안전하게 공유하기 위한 기법으로 각광 받고 있다. 하지만 기존 기법은 재암호화 키를 반복적으로 사용할 수 있어 재암호화 오남용 문제가 발생한다. 이를 해결하기 위해 조건부 프록시 재암호화 기법이 제안되었지만 조건값의 수만큼 재암호화키를 생성해야하는 부담이 있다. 본 논문에서는 재암호화 키 생성 측면에서 효율적인 조건부 프록시 재암호화 기법을 제안하였다. 제안하는 기법은 조건값의 사용을 암호화와 복호화 과정으로 제한하여 조건값이 많아지더라도 재암호화 키를 추가로 생성하지 않아도 되는 장점이 있다. Weng 등의 기법이 재암호화 키 생성에 따른 시간 복잡도가 O(n)인 것에 비해, 제안하는 기법은 O(1)의 시간 복잡도를 가진다. 또한, 제안하는 기법은 선택적 암호문 공격에 안전하도록 설계되었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.600-607
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• 2004

The paper describes the implementation of the video conferencing system using public key infrastructure which is used for user authentication and media stream encryption. Using public key infrastructure, we are able to reinforce the authentication for conference participant and block several malicious hacking while protecting conference control information. The paper shows the implementation of the transportation layer secure protocol in conformity with Korea public key authentication algorithm standard and symmetric key encryption algorithm (RC2, SEED, DES and 3DES) for media stream encryption. The feature of the paper is transportation layer secure protocol that is implemented for protection of information on a user authentication and video conference and the media streaming encryption algorithm also can be envisioned with another block encryption algorithm. The key for media streaming encryption may be safely distributed by the transportation layer secure protocol.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.563-565
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• 2008

In this paper, we construct an efficient fuzzy identity-based encryption scheme in the random oracle model. The fuzzy identity-based encryption is an extension of identity-based encryption schemes where a user's public key is represented as his identity. Our construction requires constant number of bilinear map operations for decryption and the size of private key is small compared with the previous fuzzy identity-based encryption of Sahai-Waters. We also presents that our fuzzy identity-based encryption can be converted to attribute-based encryption schemes.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.983-990
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• 2022

In this paper, we implemented a hierarchical encryption system using two-step phase-shifting digital holography(PSDH) technology based on XOR and scramble operations. The proposed encryption system is a system that authenticates access through the issuance of an encryption key for access to individual laboratories, department offices, and universities. In the encryption process, we proposed a double encryption method using XOR and scramble operation with digital technology and two-step phase-shifting digital holography with optical technology. In the two-step PSDH process, an new method of determining the reference wave intensity without measuring it by using random common object image gererated from digital encryption process was also proposed. In the decryption process, the process is performed in the reverse order of encryption process. And only when the various key information used in the encryption process is correct, the encrypted information can be decrypted, so that the user can access the desired place. That is, there is a feature that can hierarchically control the space that can be accessed according to the type of key issued in the proposed encryption system. Through the computer simulation, the feasibility of the proposed hierarchical encryption system was confirmed.

• 정보보호학회논문지
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• 제18권4호
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• pp.3-15
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• 2008

검색 가능 암호 시스템 (Searchable Encryption)은 암호화된 데이터에서 키워드를 검색하는 문제를 해결하기 위하여 2000년에 Song 등에 의해서 처음으로 제안되었다. 지금까지 대칭키 암호화 방식과 공개키 암호화 방식에 기반하는 여러 가지 검색 가능 암호 시스템이 제안되었으나, 공개키 암호화 방식에 기반한 기존의 기법들은 암호화 된 문서의 검색을 위해 서버에서 저장해야 하는 인덱스들의 크기가 키워드 개수에 비례하여 선형적으로 증가하는 단점을 가진다. 본 논문에서는 공개키 기반 검색 가능 암호 시스템에서 서버에서 저장하는 인덱스의 길이를 줄이기 위해 Bloom Filter를 적용하는 방법을 제안하고, Boneh 등이 제안한 PEKS(Public key Encryption with Keyword Search)에 제안한 방법을 적용하여, 메모리 측면에서 그 효율성을 분석한다.

• ETRI Journal
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• 제22권4호
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• pp.25-31
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• 2000

Design of secure and efficient public-key encryption schemes under weaker computational assumptions has been regarded as an important and challenging task. As far as ElGamal-type encryption schemes are concerned, some variants of the original ElGamal encryption scheme based on weaker computational assumption have been proposed: Although security of the ElGamal variant of Fujisaki-Okamoto public -key encryption scheme and Cramer and Shoup's encryption scheme is based on the Decisional Diffie-Hellman Assumption (DDH-A), security of the recent Pointcheval's ElGamal encryption variant is based on the Computational Diffie-Hellman Assumption (CDH-A), which is known to be weaker than DDH-A. In this paper, we propose new ElGamal encryption variants whose security is based on CDH-A and the Elliptic Curve Computational Diffie-Hellman Assumption (EC-CDH-A). Also, we show that the proposed variants are secure against the adaptive chosen-ciphertext attack in the random oracle model. An important feature of the proposed variants is length-efficiency which provides shorter ciphertexts than those of other schemes.