• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.251-255
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• 2008

In most file systems, if a file is deleted, only the metadata of the file is deleted or modified and the file's data is still stored on the physical media. Some users require that deleted files no longer be accessible. This requirement is more important in embedded systems that employ flash memory as a storage medium. In this paper, we propose a secure deletion method for NAND flash file system and apply the method to YAFFS. Our method uses encryption to delete files and forces all keys of a specific file to be stored in the same block. Therefore, only one erase operation is required to securely delete a file. Our simulation results show that the amortized number of block erases is smaller than the simple encryption method. Even though we apply our method only to the YAFFS, our method can be easily applied to other NAND flash file systems.

• The Transactions of the Korea Information Processing Society
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• v.7 no.6
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• pp.1874-1885
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• 2000

When a receiver of ciphertext message can not decrypt a message because he has lost his private-key, the private-key of receiver and session-key of the message should be recovered. In this paper, we developed an Encapsulation based Key Recovery System (EKRS). EKRS is a new key encapsulation based key recovery system which is characterized by secretly choice of KRA, randomized target keys. n-way recovery type, and useful for commercial key recovery. EKRS is formally specified by a pictorial model, an Extended Cryptographic Timed Petri Net (ECTPN). Secure information flow and reachability of a session-key are verified by using reachability graph of ECTPN. EKRS, executing over a Public Key Infrastructure, can be used as a security solution in Web based applications such as CALS, EC an EDI.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.3
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• pp.53-64
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• 2005

In this paper, proposes Kerberos certification mechanism that improve certification service of PKINIT base that announce in IETF CAT Working Croup. Also proposed Authentication Mechanism for reusability of Ticket that after Ticket's Lifetime is ended, message exchange that Local Client receives Remote Server's service. Since my suggestion to regional services are not described in Kerberos, authentication between regions can be performed via PKINIT(Public Key Cryptography for Initial Authentication) presented by IETF(Internet Engineering Task Force) CAT working group. The new protocol is better than the authentication mechanism proposed by IETF CAT Working group in terms of communication complexity and mechanism according to simplified Ticket issue processing.

• 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].

• Journal of Venture Innovation
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• v.2 no.2
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• pp.21-29
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• 2019

In the public certificate technology commonly used in Korea, users have a cumbersome problem of always resetting when they forget their password. In this paper, as a solution to this problem, we propose a secure authentication certificate password recovery protocol using blockchain, PKI, and DID for distributed storage. DID is a schema for protecting block ID in blockchain system. The private key used in the PKI is configured as a user's biometric, for example, a fingerprint, so that it can completely replace the memory of the complex private key. To this end, based on the FIDO authentication technology that most users currently use on their smartphones, the process of authenticating a user to access data inside the block minimizes the risk of an attacker taking over the data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.845-848
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• 2003

정보화 사회가 됨에 따라 정보의 중요성과 함께 역기능으로 인한 부작용 또한 갈수록 심각해질 수 있으며 이에 따라 정보보호 요구가 크게 늘어나고 있고 관련 정보보호제품의 수요증가가 예상되고 있다. 한편 선진각국은 OECD, APEC 등 다자간 협의를 통하여 정보 시스템의 안전과 암호정책에 관한 논의를 활발히 진행 중에 있어, 조만간 정보보호제품도 통상문제로 제기될 가능성이 다분하다. 그러나 국내 정보보호산업이 취약한 상태에 있고 정보보호의 특성상 정보보호 제품의 해외시장 의존은 바람직하지 않을 것이며 독자적인 기술력의 제품개발이 필수 불가결할 것으로 생각된다. 본 논문에서는 공중전화망(PSTN)의 전화 정보보호를 위한 디지털 보안전화기(이하 텔레가드폰)를 제안하고 이를 설계 및 구현하였다. 본 연구에서 제안한 디지털 보안전화기는 음성을 저속 압축 디지털 코드로 변환하고, 이에 국내 128 비트 블록 정보보호 알고리즘의 표준으로 정해진 SEED를 적용하여 안전한 통신이 가능하도록 하였다. 뿐만 아니라 키 복구 기능이 구현하여 개발된 시스템이 합법적 암호 접근을 허용하도록 하였다.

• Electronics and Telecommunications Trends
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• v.17 no.6 s.78
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• pp.29-38
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• 2002

XML 전자문서는 전자상거래를 위한 전자문서의 표준으로 받아 들여지고 있으며 안전한 전자상거래를 위해서는 XML 정보보호가 무엇보다도 먼저 해결되어야 한다. 본 논문에서는 인터넷 상에서 XML을 기반으로 하는 전자문서 교환 시스템의 안전한 문서 교환을 위한 정보보호 서비스 구현을 소개한다. XML 기반 전자문서 교환 시스템은 주로 인터넷에서 상거래를 위해 사용자 인증, 데이터 무결성 보장, 송수신에 대한 부인 봉쇄 등 다양한 보안 기능에 대해 필요하다. 또한 본 논문은 이러한 보안 기능을 충족시키는 XML 기반 정보보호 서비스인 ESES(ETRI Secure E-commerce Services)를 제안한다. ESES는 XML 문서 뿐 아니라 전자상거래 시 교환되는 디지털 콘텐츠를 위한 보안 서비스 제공을 목적으로 하며, 자바기반의 암호 구조를 바탕으로 XML 기반 전자서명, XML 기반 암복호, XML 기반 키 복구, 인증서 처리 기능 등을 지원한다.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.12
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• pp.569-576
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• 2013

Cloud computing has been receiving increasing attention recently. Despite this attention, security is the main problem that still needs to be addressed for cloud computing. In general, a cloud computing environment protects data by using distributed servers for data storage. When the amount of data is too high, however, different pieces of a secret key (if used) may be divided among hundreds of distributed servers. Thus, the management of a distributed server may be very difficult simply in terms of its authentication, encryption, and decryption processes, which incur vast overheads. In this paper, we proposed a efficiently data storage and recovery scheme using XOR and RAID in Hadoop environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.6
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• pp.271-288
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• 2010

In this paper, we study the dysfunctions of cryptography as dual-use goods and national domestic encryption control policies like key recovery system and decryption order. And we examine risks of the breach of the peoples' constitutional rights like the right to privacy in these policies and analyze these policies by applying the principle of the ban on the over-restriction. Finally, we propose the direction and requirements of our national domestic encryption control policy that maintains the balance of peoples' constitutional rights and investigatory powers.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.7
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• pp.311-316
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• 2013

256-bit block cipher XSB(eXtended Spn Block cipher) was proposed in 2012 and has a symmetric strucrure in encryption and decryption process. In this paper, we propose a differential fault analysis on XSB. Based on a random byte fault model, our attack can recover the secret key of XSB by using only two random byte fault injection. This result is the first known cryptanalytic result on the target algorithm.