• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2928-2940
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• 2013

Key exposure is a major threat to secure cryptosystems. To mitigate the impact caused by key-compromise attacks, a key-insulated cryptographic mechanism is a better alternative. For securing the large message communication in peer-to-peer networks, in this paper, we propose the first novel identity-based key-insulated encryption (IB-KIE) scheme with message linkages. Our scheme has the properties of unbounded time periods and random-access key-updates. In the proposed scheme, each client can periodically update his private key while the corresponding public one remains unchanged. The essential security assumption of our proposed scheme is based on the well-known bilinear Diffie-Hellman problem (BDHP). To ensure the practical feasibility, we also formally prove that the proposed scheme achieves the security requirement of confidentiality against indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2) in the random oracle model.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.24-29
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• 2009

Sahai and Waters first introduced the concept of Fuzzy Identity Based Encryption (FIBE) to provide an error-tolerance property for Identity Based Encryption (IBE) in 2005. Yang et al. extended this idea and introduced the concept of Fuzzy Identity Based Signature (FIBS) in 2008, and constructed a FIBS scheme based on Sahai and Waters's FIBE scheme. In this paper, we further formalize the notion and security model of FIBS scheme and propose a new construction of FIBS scheme based on bilinear pairing. The proposed FIBS scheme not only provide shorter public parameters, private key and signature, but also have useful structures which result in more efficient key extraction, signing and verification than that of Yang et al.'s FIBS scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3401-3420
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• 2021

We provide a traceable ciphertext-policy attribute based encryption (CP-ABE) construction for monotone access structures (MAS) based on composite order bilinear groups, which is secure adaptively under the standard model. We construct this scheme by making use of an "encoding technique" which represents the MAS by their minimal sets to encrypt the messages. To date, for all traceable CP-ABE schemes, their encryption costs grow linearly with the MAS size, the decryption costs grow linearly with the qualified rows in the span programs. However, in our traceable CP-ABE, the ciphertext is linear with the minimal sets, and decryption needs merely three bilinear pairing computations and two exponent computations, which improves the efficiency extremely and has constant decryption. At last, the detailed security and traceability proof is given.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.1
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• pp.23-33
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• 2006

Key Agreement protocols are among the most basic and widely used cryptographic protocols. In this paper we present an efficient O-based authenticated key agreement (AKA) protocol by using bilinear maps, especially well suited to unbalanced computing environments : an ID-based AKA protocol for Server and Client. Particularly, considering low-power clients' devices, we remove expensive operations such as bilinear maps from a client side. Our protocol uses signcryption and provide security in random oracle model.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.703-705
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• 2004

그룹 디지털 서명(Group Signatures)은 그룹의 회원인 서명자의 익명성을 보장하는 디지털 서명 방법이다. 최근에 이 서명방법에 비해 향상된 기능을 제공하는 추척 가능한 디지털 서명 방법이 제안되었다. 본 논문은 타원곡선 암호의 Pairing 기법으로 구현될 수 있는 Bilinear map을 이용한 추적 가능한 디지털 서명 방법을 소개한다. 이 서명 방법은 321 바이트를 차지하기 때문에 기존의 방법이 약 1238 바이트를 차지하는데 비해 효율적인 서명 방법이라 할 수 있다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.3
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• pp.101-110
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• 2003

Secure and reliable group communication is an increasingly active research area prompted by the growing popularity of many types of group-oriented and collaborative applications. The central challenge is secure and efficient group key management. While centralized methods are often appropriate for key distribution in large multicast-style groups, many collaborative group settings require distributed key agreement techniques. Most of prior group key agreement protocols have been focused on reducing the computational costs. One exception is STR protocol that optimizes communicational cost. On the other hand, it requires O(n) number of modular exponentiations. In this paper, we propose a new group key agreement protocol that modifies STR protocol by utilizing pairing based cryptography. The resulting protocol reduces computational cost of STR protocol while preserving the communication cost.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.682-691
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• 2012

Key agreement protocol is a fundamental protocol in cryptography whereby two or more participants can agree on a common conference key in order to communicate securely among themselves. In this situation, the participants can securely send and receive messages with each other. An adversary not having access to the conference key will not be able to decrypt the messages. In this paper, we propose a novel identity-based authenticated multi user key agreement protocol employing a symmetric balanced incomplete block design. Our protocol is built on elliptic curve cryptography and takes advantage of a kind of bilinear map called Weil pairing. The protocol presented can provide an identification (ID)-based authentication service and resist different key attacks. Furthermore, our protocol is efficient and needs only two rounds for generating a common conference key. It is worth noting that the communication cost for generating a conference key in our protocol is only O($\sqrt{n}$) and the computation cost is only O($nm^2$), where $n$ implies the number of participants and m denotes the extension degree of the finite field $F_{p^m}$. In addition, in order to resist the different key attack from malicious participants, our protocol can be further extended to provide the fault tolerant property.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.4
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• pp.135-140
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• 2004

The ID-based cryptosystem and Power Analysis Attack are attracting many researchers and have been developed aggressively to date. Especially, DPA (Differential Power Analysis) attack has been considered to be the most powerful attack against low power devices, such as smart cards. However, these two leading topics are researched independently and have little hewn relations with each other. In this paper, we investigate the effect of power analysis attack against ID based cryptosystem. As a result, we insist that ID-based cryptosystem is secure against DPA and we only need to defend against SPA (Simple Power Analysis).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.5
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• pp.1687-1707
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• 2022

With the development of multiuser online meetings, more group-oriented technologies and applications for instance collaborative work are becoming increasingly important. Authenticated Group Key Agreement (AGKA) schemes provide a shared group key for users with after their identities are confirmed to guarantee the confidentiality and integrity of group communications. On the basis of the Public Key Cryptography (PKC) system used, AGKA can be classified as Public Key Infrastructure-based, Identity-based, and Certificateless. Because the latter type can solve the certificate management overhead and the key escrow problems of the first two types, Certificateless-AGKA (CL-AGKA) protocols have become a popular area of research. However, most CL-AGKA protocols are vulnerable to Public Key Replacement Attacks (PKRA) due to the lack of public key authentication. In the present work, we present a CL-AGKA scheme that can resist PKRA in order to solve impersonation attacks caused by those attacks. Beyond security, improving scheme efficiency is another direction for AGKA research. To reduce the communication and computation cost, we present a scheme with only one round of information interaction and construct a CL-AGKA scheme replacing the bilinear pairing with elliptic curve cryptography. Therefore, our scheme has good applicability to communication environments with limited bandwidth and computing capabilities.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.6
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• pp.149-161
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• 2003

Partially blind signature scheme allows the signer to insert non-removable common information into his blind signature. Blind signatures providing with both users privacy and data authenticity are one of key parts of information systems, such anonymous electronic cash and electronic voting as typical examples. Partially blind signature, with which all expired e-cash but for still-alive can be removed from the banks database, copes well with the problem of unlimited growth of the banks' database in an electronic cash system. In this paper we propose an efficient ID-based partially blind signature scheme using the Weil-pairing on Gap Diffie-Hellman group. The security of our scheme relies on the hardness of Computational Diffie-Hellman Problem. The proposed scheme provides higher efficiency than existing partially blind signature schemes by using three-pass protocol between two participants, the signer and requesters also by reducing the computation load. Thus it can be efficiently used in wireless environment.