• 한국IT서비스학회:학술대회논문집
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• 2003.11a
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• pp.124-132
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• 2003

최근 급증하고 있는 전자상거래에서의 소비자피해를 줄이고 거래의 신뢰성을 높이기 위한 수단으로 온라인 에스크로 서비스가 이용되고 있으며, 관련 법제의 개정을 통한 제도 도입이 추진되고 있다. 매매당사자간 물품과 대금의 지급을 보장하는 에스크로 서비스는 전자상거래 소비자피해를 예방하고 사후적 피해를 실질적으로 구제할 수 있는 효과적인 거래안전장치임에 틀림없다. 하지만 소비자보호 측면뿐만 아니라 전자상거래의 지속적인 발전을 위해서는 관련된 제도적 보완이 필요하다. 우선, 현재 추진 중에 있는 전자상거래소보법의 개정 또는 기타 법률의 형태로 에스크로 서비스의 제도적 가이드라인을 제시하기 위한 입법화가 요구되며, 둘째, 온라인 거래의 당사자들이 누구라도 언제든지 에스크로 서비스를 이용할 수 있도록 에스크로 제도의 도입을 강제하되 그 이용 여부는 거래당사자간 교섭에 의해 결정토록 하는 방안을 고려해 볼 수 있다. 셋째, 안전한 대금지급을 위한 정보제공의 차원에서 에스크로 서비스의 이용에 관한 사항을 소비자가 알기 쉽도록 의무적으로 표시토록 하고, 넷째, 에스크로 서비스의 공신력 제고를 위해 에스크로 사업자의 자격에 관한 별도의 기준을 마련하여 규제하는 것이 바람직하다.

• Journal of the Korea Computer Industry Society
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• v.3 no.8
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• pp.1105-1116
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• 2002

This paper has presented three types of key recovery methods, which are known as key escrow, key encapsulation, and trusted third party scheme. we have analyzed the existing key recovery products, which have been developed by the advanced nations for electronic commerce and electronic government. we have also analyzed the key recovery policies proposed by the advanced nations, such as The United States of America, Great Britain, and Japan. In this paper, several key recovery policies are proposed for the e-commerce and e-government system. And we have proposed key recovery scheme for the e-commerce system utilizing the on-line secret sharing scheme based on the Internet and public bulletin board.

• 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.12 no.5
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• pp.53-61
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• 2002

In this paper, we will introduce a design of key recovery based on XML can be used in B2B environment. XML Digital Signature and XML Encryption that are defied recently as standards by W3C(World Wide Web Consortium) are deployed to sign/verify or encrypt/decrypt documents for electronic commerce and keys to store/load at/from key recovery server. The result of signature or encryption is always an XML document and all messages used in this key recovery system are also XML documents. It enables to adapt transparently this key recovery system to legacy XML applications and electronic commerce platforms based on XML. And its method for key recovery is key escrow. One of the characteristics of this key recovery is that one enterprise can recover keys of some documents for electronic commerce from external key recovery system in other enterprises related with them and also recover keys from owns.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1502-1522
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• 2019

Leakage of secret keys may be the most devastating problem in public key cryptosystems because it means that all security guarantees are missing. The forward security mechanism allows users to update secret keys frequently without updating public keys. Meanwhile, it ensures that an attacker is unable to derive a user's secret keys for any past time, even if it compromises the user's current secret key. Therefore, it offers an effective cryptographic approach to address the private key leakage problem. As an extension of the forward security mechanism in certificate-based public key cryptography, forward-secure certificate-based signature (FS-CBS) has many appealing merits, such as no key escrow, no secure channel and implicit authentication. Until now, there is only one FS-CBS scheme that does not employ the random oracles. Unfortunately, our cryptanalysis indicates that the scheme is subject to the security vulnerability due to the existential forgery attack from the malicious CA. Our attack demonstrates that a CA can destroy its existential unforgeability by implanting trapdoors in system parameters without knowing the target user's secret key. Therefore, it is fair to say that to design a FS-CBS scheme secure against malicious CAs without lying random oracles is still an unsolved issue. To address this problem, we put forward an enhanced FS-CBS scheme without random oracles. Our FS-CBS scheme not only fixes the security weakness in the original scheme, but also significantly optimizes the scheme efficiency. In the standard model, we formally prove its security under the complexity assumption of the square computational Diffie-Hellman problem. In addition, the comparison with the original FS-CBS scheme shows that our scheme offers stronger security guarantee and enjoys better performance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.2
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• pp.239-248
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• 2012

VANET (Vehicular Ad-hoc Network) is a type of MANET (Mobile Ad-hoc Network) which is the next-generation networking technology to provide communication between vehicles or between vehicle and RSU (Road Side Unit) using wireless communication. In VANET system, a vehicle accident is likely to cause awful disaster. Therefore, in VANET environment, authentication techniques for the privacy protection and message are needed. In order to provide them privacy, authentication, and conditional, non-repudiation features of the group signature scheme using a variety of security technologies are being studied. In this paper, and withdrawal of group members to avoid frequent VANET environment is suitable for vehicles produced by the group administrator for a private signing key to solve the key escrow problem of a group signature scheme is proposed. We proposed a message batch verification scheme using Bloom Filter that can verify multiple messages efficiently even for multiple communications with many vehicles.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.23-36
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• 2005

The main obstacle hindering the wide deployment of identity-based cryptosystem is that the entity responsible for creating the private key has too much power. As a result, private keys are no longer private. One obvious solution to this problem is to apply the threshold technique. However, this increases the authentication computation, and communication cost during the key issuing phase. In this paper, we propose a new effi ient model for issuing multiple private keys in identity-based encryption schemes based on the Weil pairing that also alleviates the key escrow problem. In our system, the private key of a user is divided into two components, KGK (Key Description Key) and KUD(Key Usage Desscriptor), which are issued separately by different parties. The KGK is issued in a threshold manner by KIC (Key Issuing Center), whereas the KW is issued by a single authority called KUM (Key Usage Manager). Changing KW results in a different private key. As a result, a user can efficiently obtain a new private key by interacting with KUM. We can also adapt Gentry's time-slot based private key revocation approach to our scheme more efficiently than others. We also show the security of the system and its efficiency by analyzing the existing systems.