• Proceedings of the Korea Multimedia Society Conference
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• 2003.11b
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• pp.707-710
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• 2003

인터넷은 전 세계를 연결하는 매체로서, 그 사용자가 매년 폭발적으로 증가하고 있다. 이러한 인터넷 사용자간의 자료 교환 수단으로서 전자우편은 표준이라 말할 수 있을 만큼 많이 사용되고 있다. 일반 편지에서부터 상업광고 목적의 전자우편에 이르기까지 다양한 분야에서 사용되고 있다. 하지만 이러한 전자우편에도 많은 문제가 존재한다. 기존의 전자우편은 간단한 방법으로 내용을 열람하거나 변조할 수 있어 중요한 정보나 사생활 노출의 위험에서 벗어날 수 없다. 이러한 데이터에 대한 보안이 기대에 미치지 못하고 있기 때문에 암호학적으로 강력한 전자우편 시스템의 개발이 시급하다 본 논문에서는 기본적인 정보보호 서비스 외에 기존의 전자우편 시스템에서는 제공되지 않는 배달 증명 및 내용 증명 기능을 제공하고 자바 암호 API를 사용하여 안전한 키 교환이 가능하도록 하였다.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.163-172
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• 2002

Java Card API porvide benifit for development program based on smart card using limmited resource. This APIs does not support arithmetic operations such as modular arithmetic, greatest common divisor calculation, and generation and certification of prime number, which is necessary arithmetic in PKI algorithm implementation. In this paper, we implement class BigInteger acted in the Java Card platform because that Java Card APIs does not support class BigInteger necessary in implementation of PKI algorithm.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.2
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• pp.83-92
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• 2007

In connectionless packet network, if a sender encrypts packets by block chaining mode and send it to receiver, the receiver should decrypt packets in encrypted order that is not received order. Therefore, the performance and efficiency are lowered for crypto communication system. To solve this problem, we propose packet encryption scheme for connectionless packet network that can decrypt the packets independently, even if the received order of packets are changed or packets are missed. The scheme makes new IV(Initial Vector) using IV that created by key exchange process and salt that made by random number. We propose extended Cryptoki API that added packet encryption/decryption functions and mechanism for improving convenience and performance. We implement the scheme and get result that the performance increased about $1.5{\sim}l5.6$ times compare with in case of implementing using Cryptoki API in the test environment.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.841-843
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• 2003

DRM(Digital Rights Management)은 디지털 컨텐츠의 저작권자 권리를 보호하고 인터넷상에서 안전한 거래를 보장하는 기술이다. DRM 기술에 있어서 암호 및 인증을 위한 서버 및 클라이언트 설계는 중요한 부분을 차지하여 SSL(Secure Socket Layer)은 늪은 안정성으로 인하여 네트워크 통신을 위한 프로토콜로 가장 많이 사용되고 있다. 본 논문에서는 DRM 유통 시스템에서 인증서를 기반으로 하는 SSL 보안 통신 메커니즘을 제안하고, 이를 기반으로 한 암호 및 인증 서버/클라이언트의 설계 및 구현에 관하여 기술한다. 본 논문에서 제안된 SSL보안 통신 메커니즘은 MS CryptoAPI를 사용하여 구현하였고, 인증서 기반의 보안이 필요한 다른 응용 프로그램 (Messenger. ftp)에도 쉽게 주용 시킬 수 있는 특징을 가진다.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.281-286
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• 2003

Nowadays, a patient's private medical data which is exposed to the outside world has a severe effect on not only the patient's private life but also his/her social activities and environment. So, it is important to securely protect the patient's private medical data from the illegal manipulation. This paper studies the method to store the electronic prescription information in an IC card. For that, an access control for users, such as a doctor, a nurse, a medical institute member, a pharmacy, a pharmacist, or a patient, is proposed to access the data stored in an IC card. The certificate is issued using the Crypto API of a certificate management model supported by Windows 2000. The public/private key is created by the Cryptographic Service Provider program, and the electronic prescription is signed using the digital signature. The proposed system, therefore, can improve the quality of medical services by securing the safety and integrity of the electronic prescription, stored in an IC card.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.3
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• pp.471-485
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• 2023

Recently, due to the nature of blockchain that guarantees users' anonymity, more and more cases are being exploited for crimes such as illegal transactions. However, cryptocurrency is protected in cryptocurrency wallets, making it difficult to recover criminal funds. Therefore, this study acquires artifacts from the data and memory area of a local PC based on user behavior from four browser extension wallets (Metamask, Binance, Phantom, and Kaikas) to track and retrieve cryptocurrencies used in crime, and analyzes how to use them from a digital forensics perspective. As a result of the analysis, the type of wallet and cryptocurrency used by the suspect was confirmed through the API name obtained from the browser's cache data, and the URL and wallet address used for the remittance transaction were obtained. We also identified Client IDs that could identify devices used in cookie data, and confirmed that mnemonic code could be obtained from memory. Additionally, we propose an algorithm to measure the persistence of obtainable mnemonic code and automate acquisition.