• Proceedings of the Korean Society of Computer Information Conference
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• 2018.01a
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• pp.35-36
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• 2018

에스크로는 개인 간의 물품 거래를 중개하여 허위 물품 등록 및 대금 횡령과 같은 사기를 방지하는 안전 결제 서비스이다. 그러나 신뢰할 수 없는 에스크로 서비스 사로 인한 사기 발생 및 에스크로의 서비스 구조와 같은 태생적인 한계로 인한 이용률 저하와 같은 한계점들은 건전한 사용자들의 이용률을 저하시킨다. 본 논문에서는 이런 문제점들을 극복하기 위해 블록체인 플랫폼중 하나인 이더리움을 이용하여 개선된 에스크로 서비스 모델을 제시하고자 한다.

• 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 the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1760-1768
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• 2004

A P2P is a method that can share and exchange on digital resources through a direct connection on personnel without a central server. In this paper, we apply a P2P technology to a traditional electronic commerce method so that a seller and a customer can perform a commercial transaction through a direct communication. As such a result, we propose a new e-Commerce model on P2P environment to assure fairness in commercial transactions. To achieve our goal, we put an escrow server which is responsible for guarantee fair contents delivery and payment for the contents between a seller and a customer. When a customer buys content, he first obtains reputation values implicating reliability for the content and refers to these values to determine purchase. The proposed scheme, we can improve the reliability for the purchasing content and provide the fairness to both a seller and a customer simultaneously.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.1
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• pp.20-34
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• 2009

We newly propose a multiple and unlinkable identity-based public key encryption scheme which allows the use of a various number of identity-based public keys in different groups or applications while keeping a single decryption key so that the decryption key can decrypt every ciphertexts encrypted with those public keys. Also our scheme removes the use of certificates as well as the key escrow problem so it is functional and practical. Since our public keys are unlinkable, the user's privacy can be protected from attackers who collect and trace the user information and behavior using the known public keys. Furthermore, we suggest a decryption key renewal protocol to strengthen the security of the single decryption key. Finally, we prove the security of our scheme against the adaptive chosen-ciphertext attack under the random oracle model.

• Journal of the Korea Society of Computer and Information
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• v.25 no.5
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• pp.209-216
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• 2020

As depository system for negotiation or reimbursement to the victim in criminal case is reflected to consideration for diminishing punishment and hence, it is very important in the process. According to the current law, one needs to fill out victim's personal information such as name, address, and ID number for processing depository. However, if the victim is sexual violence victim, all the personal information is covered up becoming anonymous. Therefore, it becomes difficult for the accused person to get necessary information. Such covering up action is to prevent further second damage that may be caused such as threatening for the negotiation whereas victim has no willingness to forgive the accused. However, even if the accused person regrets his/her crime and make reimbursement to the victim, as they have no personal information on the victim it becomes impossible for them to make the depository. If we apply ESCROW system here it will allow victims to avoid any direct contact with the accused person as well as preventing any privacy disclosure. Also, for the accuse person, they can show how much they regret by making depository within their capability.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.29-36
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• 2013

To accommodate the rapid growth of e-commerce transactions, non-face-to-face transactions, businesses use a wide variety of payment methods. However, many of these payment mediums are not secure as shown by increases in fraudulent transactions. In this paper, we analyze a particular e-commerce transaction medium, the Safety Transaction Service (STS). This system protects consumers through a wide variety of safeguards: safety settlement systems (escrow), consumer damage compensation insurance, payment guarantee, and secure bank settlement. In contrast to the safeguards, we identify the limitations and concerns with the STS and potential legal and political improvements. The plethora of payment methods limits the consumers ability to distinguish between the secured and unsecured transaction services. Regulation and consumer based verification of transaction services are essential to root out dangerously fraudulent systems. We propose the development of specific standards to these systems, in particular the need for consumer confirmation and clear settlement documentation. Only through the active promotion of scrutiny and improvement to STS will consumers be protected in e-commerce.

• The KIPS Transactions:PartC
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• v.18C no.6
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• pp.379-388
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• 2011

Ensuring the security of medical records is becoming an increasingly important problem as modern technology is integrated into existing medical services. As a consequence of the adoption of EMR(Electronic Medical Records) in the health care sector, it is becoming more and more common for a health professional to edit and view a patient's record. In order to protect the patient's privacy, a secure authentication model to access the electronic medical records system must be used. A traditional identity based digital certificate for the authenticity of EMR has private key management and key escrow of a user's private key. In order to protect the EMR, The traditional authentication system is based on the digital certificate. The identity based digital certificate has many disadvantages, for example, the private key can be forgotten or stolen, and can be easily escrow of the private key. Nowadays, authentication model using fingerprint recognition technology for EMR has become more prevalent because of the advantages over digital certificate -based authentication model. Because identity-based fingerprint recognition can eliminate disadvantages of identity-based digital certificate, the proposed authentication model provide high security for access control in EMR.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2271-2279
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• 2007

In this paper, we introduce the notion of certificate-based encryption in multi-receiver environment, which avoids the inherent key escrow problem while preserving the implicit certification in identity-based encryption. We also construct a highly efficient certificate-based encryption scheme for multi-receiver environment, which eliminates pairing computation to encrypt a message for multiple receivers. Moreover, the proposed scheme only needs one pairing computation for decrypting the ciphertext. We compare our scheme with the most efficient identity-based encryption scheme for multi-receiver environment proposed by Baek et.al.[1] in terms of the computational point of view, and show that our scheme provides better efficiency than Baek's scheme. Finally, we discuss how to properly transform our scheme into a new public key broadcast encryption scheme based on subset-cover framework.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2002.11a
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• pp.602-608
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• 2002

본 논문에서는 두 참여자간의 암호화 통신상에 있이 법집행기관이 정해진 확률 P에 따라 메시지를 복호화 하는 것이 가능하도록 해주는 키위탁 기법을 고려한다. 이것은 확률 P에 의해 사람들 개개인의 프라이버시와 법집행기간에 의한 개인침해란 두 주제 사이를 적절히 조절하도록 해준다. 제안된 방법은 ElGamal의 공개키 암호, 공개적으로 검증가능한 ElGamal 공개키 암호에 있어서 공통 지수부에 대한 지식 증명, 그리고 분배된 키위탁 기관들에서의 비밀공유기법 등에 바탕을 둔다. 또한 두 참여자간의 세션키를 복호화 하기 위해 필요한 각 키위탁 기관의 파라메터들은 영지식 대화형 증명 프로토콜을 통과하여야만 사용이 가능하도록 구성된다. 이와 같은 기법들을 통해 두 참여자간의 암호화된 통신에 접근 가능한 법집행기관과 암호화된 통신에 사용된 세션키를 보호하기 위한 분배된 키위탁기관들이 참여된 키위탁 기법을 고려한다.

• ETRI Journal
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• v.38 no.4
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• pp.724-734
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• 2016

To achieve confidentiality, integrity, authentication, and non-repudiation simultaneously, the concept of signcryption was introduced by combining encryption and a signature in a single scheme. Certificate-based encryption schemes are designed to resolve the key escrow problem of identity-based encryption, as well as to simplify the certificate management problem in traditional public key cryptosystems. In this paper, we propose a new certificate-based signcryption scheme that has been proved to be secure against adaptive chosen ciphertext attacks and existentially unforgeable against chosen-message attacks in the random oracle model. Our scheme is not based on pairing and thus is efficient and practical. Furthermore, it allows a signcrypted message to be immediately verified by the public key of the sender. This means that verification and decryption of the signcrypted message are decoupled. To the best of our knowledge, this is the first signcryption scheme without pairing to have this feature.