• Journal of Korea Multimedia Society
• /
• v.8 no.7
• /
• pp.974-987
• /
• 2005

As the ad hoc networks have been received a great deal of attention to not only the military but also the industry applications, some security mechanisms are required for implementing a practical ad hoc application. In this paper, we propose a security architecture in ad hoc networks for the purpose of supporting ID-based public key cryptosystems because of the advantage that ID-based schemes require less complex infrastructure compared with the traditional public key cryptosystems. We assume a trusted key generation center which only issues a private key derived from IDs of every nodes in the system setup phase, and use NIL(Node ID List) and NRL(Node Revocation List) in order to distribute the information about IDs used as public keys in our system. Furthermore, we propose a collaborative status checking mechanism that is performed by nodes themselves not by a central server in ad-hoc network to check the validity of the IDs.

• Journal of KIISE:Information Networking
• /
• v.30 no.4
• /
• pp.484-493
• /
• 2003

Proxy signature scheme is a cryptographic protocol that an original signer delegates her signing capability to a proxy signer, and then the proxy signer is able to create signatures on behalf of the original signer. In general, there is time-limit for which the signing capability of the proxy signer is valid. One of methods to limit the valid delegation time is to make public delegation information contain the expiration date of the delegation. however, in this method we cannot prevent the proxy signer from signing after the valid delegation is expired because no one knows the exact time when the proxy signer signed a message. The validity of the past legal signatures cannot be preserved in case that the proxy singer´s key is compromised during the delegation period. In this paper, we propose a new scheme, time-limited forward-secure proxy signature protocol, which prevents the proxy singer from signing after the valid delegation is expired and which preserves the validity of the past legal signatures even if the signing key is compromised. The proposed scheme does not require the exact time-information by making an original signer control time-related parameters and satisfies the forward-security property in each update-period of the proxy signing key. The time-period is determined according to the application characteristics or security policies.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.12 no.6
• /
• pp.47-58
• /
• 2002

The access control techniques, which can control unauthorized members to access to multicast service, have not been studied very often while there are a lot of on-going study on secure multicast architecture, multicast key distribution and sender authentication scheme have been studied. Multi level access control scheme in multicast can be used in a remote secure conference or to provide graduated multimedia services to each customers. In fact, multicast network has its own virtual networks according to different security levels. However, Early schemes are not effective when it protects unauthorized access in multi-access network environment. Furthermore this scheme does not provide us with hierarchical access control mechanism. This paper, therefore, proposes hierarchical access control scheme to provide the effectiveness in network layer by security level comparison. And we also suggests hierarchical key distribution scheme for multi level access control in application layer and effective hierarchical key renewal scheme in dynamic multicast environment which is easy to join and leaving the multicast group.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.21 no.1
• /
• pp.93-104
• /
• 2011

A conditional access system is an essential element in IPTV services enabling service providers to allow authorized access to their services only to paid subscribers. Currently, there are two types of IPTV service models, namely PPC (pay-per-channel) and PPV (pay-per-view). However, a more desirable model would be the flexible PPC model, in which subscribers are free to choose any combination of preferred channels and add/remove channels independently. In this paper, we first point out that a previously proposed key management scheme for F-PPC is not secure. We then propose a new conditional access system using 4-level key hierarchy to realize secure F-PPC services. Compared to existing schemes, the proposed system is very efficient, just requiring O(1) communication for key update.

• 한국공간정보시스템학회:학술대회논문집
• /
• 2007.06a
• /
• pp.318-323
• /
• 2007

모바일매핑시스템은 차량에 CCD카메라, GPS IMU등의 장비를 탑재하고 도로 및 주변지역의 영상을 획득하여 지도제작 및 도로 도로시설물의 유지관리를 위한 시스템이다. 그러나 모바일매핑시스템의 자료는 자료의 양이 방대하여 지도제작 및 시설물 관리에 사용되기 위해서는 일차적인 가공이나 편집이 필요하다. 모바일매핑시스템은 대상물의 위치 및 영상정보를 획득할 수 있는 효율적인 시스템으로 도로 시설물의 유지 관리, 수치지도의 갱신 등 여러 분야에서 활용되고 있다. 이러한 모바일매핑시스템은 CCD 카메라 영상과 차량의 위치 및 자세정보를 제공하게 되고 이는 영상안의 객체에 대한 위치정보를 제공하는데 중요한 역할을 한다. 그러므로 본 연구에서는 모바일매핑시스템을 이용하여 영상내부에 나타난 거리표의 3차원 위치를 결정하고자 한다. 또 도로관리통합시스템의 핵심 키가 되는 거리표의 3차원 정보를 자동으로 추출함으로써 모바일매핑시스템의 방대한 정보를 효율적으로 처리하기 위한 방법을 알아볼 것이다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 2006.06a
• /
• pp.623-626
• /
• 2006

위치 정보 기반 서비스는 휴대 무선 통신 기기 사용의 확대에 따라 서비스의 범위가 크게 확장될 것으로 예상되고 있다. 그러나 단순한 정보 제공이 아닌 원격 제어, 콘텐츠 서비스 등의 경우에서 위치 정보에 대한 위변조 문제와 사용자의 프라이버시 문제가 발생할 것으로 예상된다. 기존의 위치 정보 보호에 대한 연구는 프라이버시 보호 측면을 위주로 하고 있으며, 인증에 대한 연구는 특정 센싱 기술에 특화되어 있거나, 네트워크상의 DNS를 통한 논리적인 위치 인증에 치우치고 있다. 본 연구에서는 위치 정보 기반 서비스에서의 보안 요구 사항을 분석하여, 기존의 위치 정보 보호 모델을 기반으로 위치 정보를 관리하는 신뢰되는 기관의 필요성을 논하며, 이를 토대로 타임스탬프나 키 갱신을 이용하는 두 가지 프로토콜을 제안한다.

• Proceedings of the Korea Contents Association Conference
• /
• 2003.05a
• /
• pp.165-170
• /
• 2003

In this thesis, we suggest the contents transmission system applied by Encryption Module. It prevents illegal distribution and reproduction of contents and supplements the limitation of the exiting transmission systems during the transmission by providing the contents encoded by RSA encryption algorithm and XOR computation method through user-oriented browser. And at same time, it protects the copyright with typing the contents and user-oriented browser in one-to-one manner by way of using the browser to renew a encoding key as soon replay is completed.

• Journal of Korea Multimedia Society
• /
• v.8 no.5
• /
• pp.670-678
• /
• 2005

A Cellular Automaton(CA) is a dynamical system in which space and time are discrete, the state of each cell is unite and is updated by local interaction. Since the characteristics of CA is diffusion and local interaction, CA is used by crypto-systems and VLSI structure. In this study, we proposed a hash function based on the concept of 2-dimensional cellular automata and analyzed the proposed hash function.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.17 no.2
• /
• pp.73-81
• /
• 2007

We give two weaknesses of a recently proposed streamcipher MICKEY. We show time-memory-data tradeoff is applicable. We also show that the state update function reduces entropy of the internal state as it is iterated, resulting in keystreams that start out differently but become merged together towards the end.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.12 no.2
• /
• pp.153-172
• /
• 2002

In this paper, we propose an architecture and a protocol fur Secure Mobile Multicast(SMM) offering efficient and secure multicast services to many mobile nodes. In this framework, we use Indirect and Direct Service Mode adaptively, according to the movement of mobile nodes around the overlapped service area, to provide reliably secure multicast with low latency, minimum key update, and minimum data loss.