• Journal of Convergence for Information Technology
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• v.9 no.10
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• pp.9-15
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• 2019

Recently, in the field of next-generation e-commerce and finance, interest in blockchain-based technologies such as Bitcoin and Ethereum is great. Although the security of blockchain technology is known to be secure, hacking incidents / accidents related to cryptocurrencies are being issued. The main causes were vulnerabilities in the external environment, such as taking over login sessions on cryptocurrency wallets, exposing private keys due to malware infection, and using simple passwords. However, private key management recommends general methods such as utilizing a dedicated application or local backup and physical archiving through document printing. In this paper, we propose a white box password-based private key protection scheme. As a result of safety and performance analysis, we strengthened the security against vulnerability of private key exposure and proved the processing efficiency of existing protocol.

• Review of KIISC
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• v.1 no.1
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• pp.94-99
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• 1991

공개 키암호 시스템(public key dcytosystem)의 각종 방식을 설명하고 심도있는 이 론적 해석과 예제를 통한 각 암호 시스템의 타당성을 입증한다. 또한, 대칭암호 시스템 (private-key cipher systems)과 비대칭암호시스템(public-key cryptosystems)별로 나누어 인 증(authentication) 및 디지탈 서명(digital signature)에 관한 문제들을 다음 목차에 따라 연재 로 자세히 기술하고자 한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.33-38
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• 2019

In this paper, we propose a new blockchain technology that could comply with GDPR. The proposed model can prevent illegal access by controlling access to the personal information according to a access policy. For example, it can control access to the information on a role-basis and information validation period. The core mechanism of the proposed model is to encrypt the personal information with public key which is associated with users attributes policy, and then decrypt it with a private key and users attributes based on a Attribute-based Encryption scheme. It can reduce a trusted third-part risk by replacing it with a number of nodes selected from the blockchain. And also the private key is generated in the form of one-time token to improve key management efficiency. We proved the feasibility by simulating the proposed model using the chaincode of the Hyperledger Fabric and evaluate the security.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.428-439
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• 2011

The main challenge in building efficient broadcast systems is to encrypt messages with short ciphertexts. In this paper, we present a new construction based on the identity. Our construction contains the desirable features, such as constant size ciphertexts and private keys, short public keys and not fixing the total number of possible users in the setup. In addition, the proposed scheme achieves the full security which is stronger than the selective-identity security. Furthermore we show that the proof of security does not rely on the random oracles. To the best our knowledge, it is the first efficient scheme that is full security and achieves constant size ciphertexts and private keys which solve the trade-off between the ciphertext size and the private key size.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.841-850
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• 2012

Most of banks in Korea provide smartphone banking services. To use the banking service, public key certificates with private keys, which are stored in personal computers, should be installed in smartphones. Many banks provides intermediate servers that relay certificates to smartphones over the Internet, because the transferring certificates via USB cable is inconvenient. In this paper, we analyze the certificate transfer protocol between personal computer and smartphone, and consider a possible attack based on the results of the analysis. We were successfully able to extract a public key certificate and password-protected private key from encrypted data packets. In addition, we discuss several solutions to transfer public key certificates from personal computers to smartphones safely.

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.317-322
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• 2005

The existing certificate based authentication or identification just verifies whether the owner of private key corresponding to public key of certificate is the DN user set in the user field in the certificate or not, then we cannot find out who is the actual private key owner in a real world. To make up for this weak points, the method to insert the identification number like the resident registration number into the certificate extension field is applied as a technical standard to current domestic PKI system. In this paper, we propose the ECC based integrated identification, identification number checking and key management protocol providing user validation during the login.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.4
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• pp.33-46
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• 2000

IPsec is a protocol suite to protect the data communication between computers on internet and many VPNs(Virtual Private Networks) use IPsec protocol. IKE protocol is used to exchange keys in IPsec. Formal analysis method is used increasingly in computer science to increase the reliability of a system. In this paper, the IKE protocol is analyzed formally. This paper shows that IKE with Authentication with Signature and Authentication with Pre-Shared Key is safe, but Authentication with Public Key Encryption and A Revised Method of Authentication with Public Key Encryption are safe only with the assumption that a participant has the correct public key of the correspondent. To make sure that a participant has the correct public key of the correspondent, the usage of certificate is recommended.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.1
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• pp.11-20
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• 2002

In 1998, A. Young and M. Yung proposed the auto-recovery auto-certificate cryptosystem in public key infrastructure. We propose the new recoverable cryptosystem in public key infrastructure which is designed with the concept of A. Young et al's auto-recovery auto-certificate cryptosystem. It has the private/public key pairs of the user and the master private/public key pairs of the escrow authority. It is based on RSA cryptosystem and has efficiency and security.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.1
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• pp.41-55
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• 2007

The certificate is used to confirm and prove the user's identity in online finance and stocks business. A user's public key is stored in the certificate(for e.g., SignCert.der) and the private key, corresponding to public key, is stored in the private key file(for e.g., SignPri.key) after encryption using the password that he/she created for security. In this paper, we show that the certificate, deleted by the commercial certificate software, can be recovered without limitation using the commercial forensic tools. In addition, we explain the problem that the private key encryption password can be detected using the SignCert.der and the SignPri.key in off-line and propose the countermeasure about the problem.

• Journal of Korea Multimedia Society
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• v.10 no.12
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• pp.1655-1662
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• 2007

Although the PKl-based user authentication solution has been widely used, the security of it can be deteriorated by a simple password. This is because a long and random private key may be protected by a short and easy-to-remember password. To handle this problem, many biometric-based user authentication solutions have been proposed. However, protecting biometric data is another research issue because the compromise of the biometric data will be permanent. In this paper, we present an implementation to improve the security of the typical PKI-based authentication by protecting the private key with a fingerprint. Compared to the unilateral authentication provided by the typical biometric-based authentication, the proposed solution can provide the mutual authentication. In addition to the increased security, this solution can alleviate the privacy issue of the fingerprint data by conglomerating the fingerprint data with the private key and storing the conglomerated data in a user-carry device such as a smart card. With a 32-bit ARM7-based smart card and a Pentium 4 PC, the proposed fingerprint-based PKI authentication can be executed within 1.3second.