• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.565-573
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• 2014

We have various e-commerce like on-line banking, stock trading, shopping using a PC or SmartPhone. In e-commerce, two parties use the certificate for identification and non-repudiation but, the attack on the certificate user steadily has been increasing since 2005. The most of hacking is stealing the public certificate and private key files. After hacking, the stolen public certificate and private key file is used on e-commerce to fraud. Generally, the private key file is encrypted and saved only with the user's password, and an encrypted private key file can be used after decrypted with user password. If a password is exposed to hackers, hacker decrypt the encrypted private key file, and uses it. For this reason, the hacker attacks user equipment in a various way like installing Trojan's horse to take over the user's certificate and private key file. In this paper, I propose the management method to secure private key of PKI using One Time Password certification technique. As a result, even if the encrypted private key file is exposed outside, the user's private key is kept safely.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.223-233
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• 2014

As a broadcast message authentication method in wireless sensor networks, ${\mu}$TESLA enables sensor nodes efficiently authenticate message from base station (BS). However, if we use ${\mu}$TESLA that has very short length of key slot in unattended wireless sensor network (UWSN), sensors may calculate a huge amount of hashs at once in order to verify the revealed secret key. In contrast, if we set the length of ${\mu}$TESLA's key slot too long in order to reduce the amount of hashs to calculate, BS should wait out the long slot time to release key. In this paper, we suggest variable key slot ${\mu}$TESLA in order to mitigate the problem. As showing experiment results, we prove that our suggestion improve sensor node's response time and decrease of number of hash function calculation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.3
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• pp.45-55
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• 2003

Wireless LAM has the advantage of extension, flexibility and easiness of installation and maintenance. However, due to the characteristics of wireless media, it is vulnerable to security attacks. PKI(Public Key Infrastructure) is estimated to be a good solution offering security function to wireless LAM including global roaming. It offers high security functions as authentication confidentiality and digital signature while it generates big overheads such as CRL search and certificate verification. The overheads can not be avoided during the initial authentication. However, when we consider the case of handoff, it can be minimized through the fast handoff. In this paper, we design a fast handoff authentication mechanism based on PKI in the wireless LAM and analyze the performance of the scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.5
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• pp.779-790
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• 2022

Fuzzy extractor is a biometric encryption that generates keys from biometric data where input values are not always the same due to the noisy data, and performs authentication securely without exposing biometric information. However, if a user registers biometric data on multiple servers, various attacks on helper data which is a public information used to extract keys during the authentication process of the fuzzy extractor can expose the keys. Therefore many studies have been conducted on reusable fuzzy extractors that are secure to register biometric data of the same person on multiple servers. But as the key length increases, the studies presented so far have gradually increased the number of key recovery processes, making it inefficient and difficult to utilize in security systems. In this paper, we design an efficient and reusable fuzzy extractor based on LWE with the same or similar number of times of the authentication process even if the key length is increased, and show that the proposed algorithm is reusably-secure defined by Apon et al.[5].

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.813-816
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• 2001

다양한 도메인에 있어서 이동 호스트의 서비스 접근은 이동성 계약에 의한 흠 도메인과 도메인간 인증에 의하여 이루어지고 있다. 그러나 다양한 서비스 제공자와 서비스들 그리고 수많은 이동 사용자들에게 있어서 홈 도메인에 의존 한 이동성 계약은 비 효율적이며 실용적이지 못한다. 본 논문에서는 티켓에 기반 한 효율적인 지불 프로토콜을 제안한다. 제안된 티켓 기반 지불 프로토콜은 공개키 암호 시스템에 기반 하여 비교하여 개선된 안전성과 확장성을 제공한다. 또한 소액 지불 기법에 기반하기 때문에 사용자는 정확히 자신이 제공 받은 서비스의 만큼의 지불을 하게 된다.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.5
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• pp.284-290
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• 2002

We propose a new authenticated encryption scheme that does not require any block encryption algorithm. Our scheme is based on the Horster-Michels-Petersen authenticated encryption scheme, and it uses a technique in the Bae~Deng signcryption scheme so that the sender's signature can be verified by an arbitrary third party. Since our scheme does not use any block encryption algorithm, we can reduce the code size in its implementation. The computation and communication costs of the proposed scheme are almost the same as those of the Bao-Deng scheme that uses a block encryption algorithm. Our scheme also satisfies all the security properties such as confidentiality, authenticity and nonrepudiation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.5
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• pp.30-39
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• 2008

This paper proposes a secure and efficient handover authentication protocol in VANET supporting fast mobility. Although the existing schemes commonly use the hash function or XOR operation to be suitable for a light-weight mobile, it does not support the security feature such as PBS. To solve this security problem, another protocol utilizing the CGA technology is proposed but it is vulnerable to the DoS attack due to a number of exponent operations. The proposed protocol using a light-weight Diffie-Hellman provides security features and performs a reduced number of exponential operation at the MN than the existing scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.3-13
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• 2002

There are cases that revoke the certification because of disclosure of private key, deprivation of qualification and the expiration of a term of validity on PKI. So, a user has to confirm the public key whether valid or invalid in the certification. There are many methods such as CRL, Delta-CRL, OCSP for the cert-validation of certification. But these methods have many problems, which cause overload traffic on network and the CRL server because of realtime processing for cert-validation of certification. In this paper we proposed cert-validation of certification improvement method based on FM Subcarrier Broadcasting, which solved problems that are data integrity by different time between transmission and receiving for CRL, and overload traffic on network and the CRL server the realtime management.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.435-436
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• 2014

소프트웨어의 불법 복제 및 인증을 거치지 않은 부정 사용 등이 큰 문제가 되고 있다. 소프트웨어 부정 사용을 막기 위해 usb 인증, 시리얼 키 인증, 서버접속을 통한 인증 등 다양한 방법들이 존재해 왔다. 그러나 이러한 기술들의 우회 방법들이 상당수 공개된 실정이다. 본 연구에서는 보다 강화된 인터넷 인증 기반의 불법 사용 방지 기술을 제안하고자 한다. 뿐만 아니라 소프트웨어를 사용해 만들어 낸 2차 창작물 또한 보호하는 방법을 제시하고자 한다.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.3
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• pp.91-98
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• 2022

With the recent increase in interest in metaverse in which virtual and physical spaces are digitally fused, many activities in physical spaces are expected to take place in web-based virtual spaces. Therefore, there is a need for research on a self-sovereign identity system that can secure privacy and mutual trust in a DID(decentralized identifier)-based virtual space environment. We, in this paper, developed and validated a reliable communication method consisting of DIDComm messages, a procedure for generating distributed identifiers, asymmetric keys, and DID documents based on Hyperledger Indy and DIDComm open sources. The developed communication method can be applied to verify each other by exchanging additional information and verifiable credentials for trust among communication participants.