• ETRI Journal
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• v.38 no.1
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• pp.123-132
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• 2016

The Boneh, Goh, and Nissim (BGN) cryptosytem is the first homomorphic encryption scheme that allows additions and multiplications of plaintexts on encrypted data. BGN-type cryptosystems permit very small plaintext sizes. The best-known approach for the expansion of a message size by t times is one that requires t implementations of an initial scheme; however, such an approach becomes impractical when t is large. In this paper, we present a method of message expansion of BGN-type homomorphic encryption using composite product pairing, which is practical for relatively large t. In addition, we prove that the indistinguishability under chosen plaintext attack security of our construction relies on the decisional Diffie-Hellman assumption for all subgroups of prime order of the underlying composite pairing group.

• Journal of Digital Contents Society
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• v.5 no.1
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• pp.1-6
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• 2004

Electronic cash is used as a payment tool for contents purchase in mobile electronic commerce environment. In order to protect customer`s privacy, we use blind signature. Blind signature has an anonymity property since it does not allow connection between customer`s ID and customer`s message. In this paper, we propose an blind signature scheme using elliptic curve algorithm based on Cap Diffie-Hellman Problem. Proposed scheme efficiently improved against existing blind signature scheme by reducing communication and computation time of the process.

• The Transactions of the Korea Information Processing Society
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• v.5 no.8
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• pp.2083-2090
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• 1998

In this paper, we propose two authentication exchange schemes which combine public key-based mutual authentication with a Diffie-Hellman key derivation exchange. The security of key exchange of the proposed schemes depends on the discrete logarithm problem. The ,securtly of the etity authentication depends on that of the signature mechanism to be used in the proposed scheme. In comparisun with the Kerberos, X.509 exchanges, and ISO 3-way authentication protocol, the proposed schemes are not only simple and efficient. but also are resistant to the full range of replay and interceptiun attacks.

• The Transactions of the Korea Information Processing Society
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• v.6 no.12
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• pp.3613-3621
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• 1999

In this paper, we analyzed the suity of key distribution protocol based on discrete logarithm for the purpose of designing key distribution protocol systematically. We also propose the efficient key agreement protocol with direct authentication. In comparison with Station-to-Station protocol, it provides the direct authentication using the Diffie-Hellman problem without signature.

• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.60-70
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• 2021

In this paper we study the problem of implementation of security issues of blue tooth, especially secure simple pairing, with the help of an efficient four user authenticated key (4UAK) for an elliptic curve cryptography (ECC). This paper also deals with the design, implement and performance evaluation of secure simple pairing (SSP) using an elliptic curve cryptography, such as Diffie Hellman protocol when four users are involved. Here, we also compute the best, worst and average case step counts (time complexities). This work puts forth an efficient way of providing security in blue tooth. The time complexity of O(n⁴) is achieved using Rabin Miller Primality methodology. The method also reduces the calculation price and light communication loads.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1083-1085
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• 2010

상호간의 보안 통신을 위해서는 서로간의 안전한 비밀키 교환이 이루어져야 한다. 이를 보장하기 위해서는 안전한 키교환 프로토콜이 사용되어야 한다. 키교환 프로토콜은 안전성을 보장함과 동시에 키의 신선도와 확신에 대한 요구사항을 모두 만족시켜야한다. 현재 대표적인 키교환 프로토콜인 Diffie-Hellman을 기본으로 하는 다양한 프로토콜이 연구 및 개발되고 있다. 최근에 연구된 EKE-E(Encrypted Key Exchange-Efficient) 프로토콜은 Diffie-Hellman 알고리즘을 통한 키교환을 제공하며 man-in-the-middle공격과 오프라인 사전공격에 대한 안정성을 보장한다. 하지만 재전송 공격에 취약성을 가진다. 본 논문에서는 최근에 제안된 키교환 프로토콜인 EKE-E의 안전성을 만족하며 재전송공격에 안전한 프로토콜을 제안한다. 동시에 연산을 줄여 보다 성능을 향상시킨다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1109-1122
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• 2016

Certificateless public key cryptography is a technique that can solve the certificate management problem of a public key cryptosystem and clear the key escrow issue of ID-based cryptography using the public key in user ID. Although the studies were actively in progress, many existing schemes have been designed without taking into account the safety of the secret value with the decryption key exposure attacks. If previous secret values and decryption keys are exposed after replacing public key, a valid private key can be calculated by obtaining the partial private key corresponding to user's ID. In this paper, we propose a new security model which ensures the security against the key exposure attacks and show that several certificateless public key encryption schemes are insecure in the proposed security model. In addition, we design a certificateless public key encryption scheme to be secure in the proposed security model and prove it based on the DBDH(Decisional Bilinear Diffie-Hellman) assumption.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.545-555
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• 2004

Proxy signature scheme allow a designated proxy person to sign a message on behalf of the original signer. Partially blind signature scheme allows the signer to insert non-removable common information into his blind signature. Proxy signature and partially blind signature are very important technologies in secure e-commerce. In this paper we propose new proxy signature scheme and ID-based partially blind signature scheme using bilinear pairing. further combining them, we propose a proxy partially blind signature scheme. The security of our schemes relies on the hardness of Computational Diffie-Hellman Problem. If we removing common information form propose ID-based partially blind signature scheme and proxy partially blind signature scheme, then they become variants of ID-based blind signature scheme and proxy blind signature scheme of Zhangs respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.581-583
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• 2017

Elliptic curve cyptography is relatively a current cryptography based on point arithmetic on elliptic curves and the Elliptic Curve Discrete Logarithm Problem (ECDLP). This discrete logarithm problems enables perfect forward secrecy which helps to easily generate key and almost impossible to revert the generation which is a great feature for privacy and protection. In this paper, we provide a lightweight Elliptic Curve Diffie-Hellman (ECDH) Key exchange generator that creates a 163 bit long shared key that can be used in an Elliptic Curve Integrated Encryption Scheme (ECIES) as well as for key agreement. The algorithm uses a fast multiplication algorithm that is small in size and also implements the extended euclidean algorithm. This proposed architecture was designed using verilog HDL, synthesized with the vivado ISE 2016.3 and was implemented on the virtex-7 FPGA board.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3086-3092
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• 2014

The FTP that provides file transfer capabilities to/from another station cannot provides data confidentialities. The FTPS and SFTP can support a security functionalities. The FTPS needs a SSL layer and SFTP use a functions of SSH. And therefore the FTPS or SFTP needs an additional modules such as SSL or SSH. In this paper, we propose a new Secured FTP protocol that can support the security functions without extra security system. The Secured FTP uses Diffie-Hellman key agreement algorithm for shared secret key generation and AES-Counter algorithm for data encryption algorithm. Our designed Secured FTP is implemented in Linux environments and the proper operations of implemented Secured FTP is verified.