• Journal of KIISE:Computer Systems and Theory
• /
• v.34 no.11
• /
• pp.581-588
• /
• 2007

In Digital Right Management, symmetric cipher is used for content encryption to reduce encryption cost, AES, advanced encryption standard is usually used to multimedia encryption under desktop environment because of its reasonable security level and computation cost. But mobile handheld device often uses slow speed processor and operates under battery-powered environment. Therefore it requires low computation cost and low energy consumption. This paper proposes new stream cipher scheme which combines pseudo random number generator(PRNG) and dynamically generated permutations. Proposed scheme activates PRNG and generates original key streams. Then it generates extended key streams by applying permutation to original sequence. These extended key streams are XORed with plaintext and generate ciphertext. Proposed scheme reduces the usage of PRNG. Therefore this scheme is fast and consumes less energy in comparison with normal stream cipher. Especially, this scheme shows great speed up (almost 2 times) than normal stream cipher scheme in random access.

• The KIPS Transactions:PartC
• /
• v.16C no.3
• /
• pp.335-346
• /
• 2009

Mobile environments are evolving the main communication environment as a develops of communication technology. In mobile environments, sensitive information can be compromised on-line, so demand for security has increased. Also, mobile devices that provide various services are in danger from malware and illegal devices, phishing and sniffing etc, and the privacy. Therefore, MTM(Mobile Trusted Module) is developed and promoted by TCG(Trusted Computing Group), which is an industry standard body to enhance the security level in the mobile computing environment. MTM protects user privacy and platform integrity, because it is embedded in the platform, and it is physically secure. However, a security approach is required when secret data is migrated elsewhere, because MTM provides strong security functions. In this paper, we analyze the TCG standard and migration method for cryptographic key, then we propose a secure migration scheme for cryptographic key using key Backup/Recovery method.

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

• Journal of the Institute of Convergence Signal Processing
• /
• v.21 no.4
• /
• pp.202-208
• /
• 2020

Recently, the importance of non-face-to-face has been emphasized due to COVID-19, and the use of sharing spaces is also expanding. The use of uncontact check-in technology for access control of sharing spaces reduces waiting time and optimizes workers' efficiency, resulting in operational cost savings. In this paper, we propose a sharing space access management system based on a mobile key and RCU (Room Control Unit), access to the facility using a mobile key, and monitor the facility using an RCU. Proposal system is for shared accommodation, rental field (residence, sale-selling hotel), shared office, etc. when there is a one-time visitor on a specific day and time, the corresponding password is delivered to the mobile platform to expose and key the existing password. It is supported by a field-adaptive system that can reduce discomfort such as delivery. In order to test the operation of the proposed integrated system, tests were conducted according to scenarios to understand the overall status of the user's reservation, check-in, and check-out, and a 100% success rate was derived for each item by setting performance indicators to prove test reliability.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.6
• /
• pp.137-145
• /
• 2013

Recently most mobile devices have soft keyboards on their LCD touch screens. Because of the tiny size of the touch screen of the soft keyboard, adjacent keys are mistakenly typed. Also utilizing a key for multiple key inputs causes key type errors. In this paper, we proposed an algorithm to recommend proper words to the user while the user continues to type keys, which helps to easily correct key type errors. In addition, we presented a soft keyboard called MissLess which implemented the recommendation algorithm. We evaluated recommendation performance of MissLess keyboard through experiments by using 3 test sets. The test results showed that the success ratio of recommendation reached up to about 90% although there were some differences between results. However it is needed to be considered that we recommended 4 words for an input word in this experiments.

• Proceedings of the Korean Information Science Society Conference
• /
• 2001.10a
• /
• pp.673-675
• /
• 2001

본 논문에서는 PC, 웹, 모바일 환경을 지원하는 글로벌 Peer-to-Peer 엔진에서 인증, 기밀성 및 무결성을 제공하기 위해 암호화/복호화에 필요한 공개키 쌍의 생성/분배/관리 기능을 지원하는 보안 관리자의 설계에 대하여 기술한다. 기존의 Peer-to-Peer 시스템이 단지 인증기관이 발행한 인증서에 의한 공개키의 분배를 지원하는데 비해 제안된 보안 관리자는 인증서뿐만 아니라 인증서가 아닌 다른 전송매체에 의해 분배된 공개키 또한 저장/관리할 수 있는 기능을 제공한다. 이것은 기존의 시스템이 인증서를 발급 받기 위해서 복잡하고 번거로운 신원 확인과 사용료를 부담하는 것에 비해 간편하게 키를 공유하여 보안을 적용시킬 수 있다. 이를 위해 본 논문에서는 키링(Key Rings)이라는 개념을 도입하는데 이는 각 피어에 해당하는 다수의 공개키/개인키를 저장 및 관리란 수 있는 한 쌍의 자료구조로써 제공된다. 또한 본 논문은 이렇게 저장/관리되는 다수의 공개키를 선택하여 사용하기 위한 알고리즘을 제시한다. 제안된 키 링을 사용하는 방식은 인증서를 사용하는 클라이언트/서버 형태의 Peer-to-Peer 보다 순수한 Peer-to-Peer 모델에 근접한 형태라고 볼 수 있다.

• The KIPS Transactions:PartC
• /
• v.15C no.3
• /
• pp.167-172
• /
• 2008

Fingerprinting scheme supports the copyright protection to track redistributors of digital content using cryptographic techniques. Fingerprinting schemes should guarantee buyer's anonymity and asymmetry for their privacy. Most of known fingerprinting schemes adopt public-key cryptosystems to achieve asymmetry and discrete logarithm problem or graph isomorphism problem to achieve anonymity. However, these schemes are not suited in mobile environment because of the drawbacks of requiring high computational complexity. In this paper, we propose an efficient fingerprinting scheme for mobile environment to provide not only asymmetry of the protocol but also transaction anonymity of the buyer. By employing symmetric encryption to encrypt the digital content and adopting agent to perform the protocols, the efficiency of the proposed scheme is improved.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2008.10a
• /
• pp.34-37
• /
• 2008

본 연구에서는 기존의 키패드 조작방식에 익숙해져 있던 모바일 폰 이용자가 새로운 터치스크린 모바일 폰으로 기종을 변경하였을 때 생성하는 멘탈모델의 특징에 대하여 고찰하였다. 먼저, 터치스크린 모바일 폰의 기능 가운데서 가장 사용 빈도가 높은 상위 7개의 기능에 대한 실험과제를 설정하여 비디오 관찰실험을 실시하였다. 다음으로 수집된 데이터를 프로토콜 분석법을 이용하여 사용자의 조작과 관련된 사고의 변용과정을 분석하였다. 분석결과 키패드 조작방식에 익숙해져 있던 피험자들은 실험이 거듭될수록 새로운 터치스크린 모바일 폰의 조작과정에 적응하기 위하여 버튼이나 화면에 탭, 더블 탭 등 컴퓨터 운영시스템(윈도우)과 웹 브라우저 상의 내비게이션과 관련된 지식을 이용하여 멘탈모델을 수정하려는 경향이 있었다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2014.04a
• /
• pp.322-324
• /
• 2014

모바일 환경이 발달함에 따라서 사용자의 개인 모바일 기기에 저장되었던 민감한 개인정보 및 기업의 비밀과 같이 기밀성을 필요로 하는 데이터의 누출 사고가 빈번히 발생하고 있다. 본 논문에서는 모바일 기기의 데이터를 지정된 장소에서만 안전히 사용할 수 있도록 하는 기법을 제안한다. 제안된 기법은 공개키 암호화 시스템을 바탕으로 지정된 장소에서만 발행되는 키를 통해서만 모바일 기기의 접근이 가능하게 함으로써 데이터 사용 위치를 강제하고, 의도하지 않은 데이터 누출을 방지한다.

• Journal of Digital Convergence
• /
• v.10 no.6
• /
• pp.247-251
• /
• 2012

Tree-based Group Diffie-Hellman (TGDH) is one of the efficient group key agreement protocols to generate the GK. TGDH assumes all members have an equal computing power. As one of the characteristics of distributed computing is heterogeneity, the member can be at a workstation, a laptop or even a mobile computer. Therefore, the group member sequence should be reordered in terms of the member's computing power to improve performance. This research proposes a reordering of members in the group key generation tree to enhance the efficiency of the group key generation.