• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.6
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• pp.1091-1102
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• 2014

The power analysis attack is a cryptanalytic technique to retrieve an user's secret key using the side-channel power leakage occurred during the execution of cryptographic algorithm embedded on a physical device. Especially, many power analysis attacks have targeted on an exponentiation algorithm which is composed of hundreds of squarings and multiplications and adopted in public key cryptosystem such as RSA. Recently, a new correlation power attack, which is tried when two modular multiplications have a same input, is proposed in order to recover secret key. In this paper, after reviewing the principle of side-channel attack based on input collisions in modular multiplications, we analyze the vulnerability of some exponentiation algorithms having regularity property. Furthermore, we present an improved exponentiation countermeasure to resist against the input collision-based CPA(Correlation Power Analysis) attack and existing side channel attacks and compare its security with other countermeasures.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.637-639
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• 2015

TELNET은 사용자가 컴퓨터에 원격 접속할 때 사용하기 위한 프로토콜이다. TELNET은 사용자 계정과 비밀번호 등 모든 데이터를 평문으로 전송하여 기밀성과 무결성이 보장되지 않고 서버를 인증하는 과정이 없어 네트워크 공격에 취약하다는 문제가 있다. 이 문제를 해결하기 위해 Kerberos, SSL/TLS와 같은 보안 프로토콜 기반에서 TELNET을 동작시키거나 SSH을 통해 원격 접속하는 방법이 있다. 하지만 이 방법들은 별도의 보안 프로토콜이 필요하다는 단점이 있다. 본 논문에서는 추가적인 프로토콜을 사용하지 않고 TELNET 자체에서 보안 기능을 지원하는 STELNET(Secured TELNET)을 제안하였다. STELNET에서 클라이언트는 인증서와 전자서명을 이용하여 서버를 인증한다. 이후 서버와 클라이언트는 키 교환을 통해 공유된 키로 암호화 된 데이터와 HMAC을 전송한다. 결과적으로 STELNET은 신뢰하는 서버와의 접속을 지원해주고, 데이터의 암호화로 기밀성을 보장하며 HMAC을 사용하여 무결성을 보장한다.

• Journal of Industrial Convergence
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• v.22 no.2
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• pp.63-71
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• 2024

Conventional methods like PIN used in conventional smartphone form factor have not considered the variation in display structure or screen size. As a result, when applied to recent variable display-based smartphones, the secret information input unit may get reduced or enlarged, leading to vulnerabilities for social engineering attacks due to deformation of the display area. This study proposes a secure keypad that responds to changes in display size in rollable and bendable smart phones. Firstly, the security problems that may arise when applying classical authentication methods to new form factors were analyzed, and corresponding security requirements were derived. The proposed security keypad addresses the key input error problem that can occur when the screen size is small. The arrangement and size of keys can be deformed with the spacing suitable for input depending on the display size of rollable and bendable smartphones. The study also considered the problem of leaking input information for social engineering attacks by irregularly distributing key input coordinates. The proposed method provides better user experience and security than existing methods and can be used in smartphones of various sizes and shapes.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1119-1122
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• 2002

본 논문에서는 Ford와 Kaliski[6]가 제안한 패스워드 은닉 기술을 적용하여 클라이언트와 서버의 은닉 변수로 은닉된 값을 서버가 패스워드 검증자로 사용하는 새로운 패스워드 기반 키 교환 프로토콜을 제안한다. 제안하는 프로토콜은 패스워드 검증자를 비밀리에 보관하여야하는 다른 검증자 기반 방식과 달리 클라이언트와 서버의 은닉 변수가 적용된 검증자를 사용하여 서버의 패스워드 검증자에 대한 안전성을 증가시켰다. 또한 Nyberg-Ruppel 방식[4]을 적용하여, 한번의 통신으로 사용자 인증과 키 교환을 할 수 있다. 본 논문에서 제안하는 프로토콜 안전성은 이산대수문제인 DLP(Discrete logarithm Problem)와 DHP(Diffie-Hellman Problem)[6]에 의존한다. 따라서 DLP와 DHP의 가정하에, 제안된 프로토콜은 오프라인 사진공격(off-line dictionary attack), 서버 데이터 도청(server data eavesdropping), 전향적 안전성(forward secrecy), Denning-Sacco 공격[1]에 대하여 안전하다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1388-1397
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• 2015

Recently, an application business model was proposed to implement an M-coupon system using the NFC-based mobile devices. In this paper, the security requirements were surveyed for a secure M-coupon system and to analyze the threats on the existing NFC-based M-coupon protocols. After considering the implementation efficiency and security, this paper presents a novel M-coupon protocol based on the Diffie-Hellman key agreement scheme. This protocol can be an alternative to solve the security problems related to the PKI (Public Key Infrastructure) and secret key distribution. Furthermore, this M-coupon protocol is designed to provide user authentication and counteract the relay attack.

• The KIPS Transactions:PartC
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• v.16C no.4
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• pp.439-448
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• 2009

The development of wireless communications provides mobility and accessibility to the wire communication users. Wireless sensor network is one of the leading wireless communication techniques. The security mechanism for wired network communication cannot be applied to wireless sensor network because of the limited resource and computing capability of nodes. Furthermore, communication errors frequently occur and the speed is low. Thus, efficient key management scheme is required in low-speed environment. In this paper, we proposed an efficient and secured master key-based scheme compared to the existing scheme. The advantage of our scheme is that establishing and renewing the pair-wise key is possible. In addition, it provides functions such as establishing group keys and renewing it. Furthermore, adding nodes is enabled through our scheme. The master key-based scheme can be applied to military operations and to radio communications for confidential communications.

• Journal of the Korea Society of Computer and Information
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• v.28 no.5
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• pp.67-74
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• 2023

In this paper, we analyze the authentication protocol for DRM proposed by Hussain et al. in 2022, and present an improved solution. Hussain et al. argued that their authentication protocol guarantees man-in-the-middle attack, replay attacks, and mutual authentication. However, as a result of analyzing Hussain et al.'s authentication protocol in this paper, Hussain et al.'s authentication protocol still has an insider attack problem, a problem with Yu et al.'s authentication protocol that they pointed out. For this reason, when an inside attacker acquires information on a mobile device, a user impersonation attack was also possible. In addition, there were problems with the user's lack of ID format verification and the problem of the secret key mismatch of the digital contents between the server and the user. Therefore, this paper proposes an improved solution to solve these problems. As a result of analysis in this paper, the improved solution is safe from various attacks such as smart card attack, insider attack, and password guessing attack and can safely authenticate users of DRM.

• Journal of Broadcast Engineering
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• v.18 no.5
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• pp.758-770
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• 2013

In a Broadcast Encryption System, a sender sends an encrypted message to a large set of receivers at once over an insecure channel and it enables only users in a target set to decrypt the message with their private keys. In 2005, Boneh et al. proposed a fully collusion-resistant public key broadcast encryption in which the ciphertext and the privatekey sizes are constant. In general, pairing-based broadcast encryption system is efficient in bandwidth and storing aspects than non-pairing based broadcast encryption system, however, it requires many computational costs that resource-constrained devices is not suit to be applied. In this paper, we propose a Broadcast Encryption scheme(called BEWD) that user can decrypt a ciphertext more efficiently. The scheme is based on Boneh et al.scheme. More precisely, it reduces receiver's computational costs by delegating pairing computation to a proxy server which computation is required to receiver in Boneh et al.scheme. Furthermore, the scheme enables a user to check if the proxy server compute correctly. We show that our scheme is secure against selective IND-RCCA adversaries under l-BDHE assumption.

• 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.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.3
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• pp.3-16
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• 2006

Encipherment in existing OS(Operating Systems) has typically used the techniques which encrypt and decrypt entirely a secret file at the application level with keys chosen by user In this mechanism it causes much overhead on the performance. However when a security-classified user-process writes a secret file, our proposed mechanism encrypts and stores automatically and efficiently the file by providing transparency to the user at the kernel level of Linux. Also when the user modifies the encrypted secret file, this mechanism decrypts partially the file and encrypts partially the file for restoring. When user reads only the part of the encrypted file, this mechanism decrypts automatically and partially the file. Therefore our proposed mechanism provides user much faster enciphering speed than that of the existing techniques at the application level.