Hoonjung Lee

Conditional privacy preserving security protocol for NFC applications

In recent years, various mobile terminals equipped with NFC (Near Field Communication) have been released. The combination of NFC with smart devices has led to widening the utilization range of NFC. It is expected to replace credit cards in electronic payment, especially. In this regard, security issues need to be addressed to vitalize NFC electronic payment. The NFC security standards currently being applied require the use of users public key at a fixed value in the process of key agreement. The relevance of the message occurs in the fixed elements such as the public key of NFC. An attacker can create a profile based on users public key by collecting the associated messages. Through the created profile, users can be exposed and their privacy can be compromised. In this paper, we propose conditional privacy protection methods based on pseudonyms to solve these problems. In addition, PDU (Protocol Data Unit) for conditional privacy is defined. Users can inform the other party that they will communicate according to the protocol proposed in this paper by sending the conditional privacy preserved PDU through NFC terminals. The proposed method succeeds in minimizing the update cost and computation overhead by taking advantage of the physical characteristics of NFC1.

Enhanced ID-Based authenticated key agreement protocols for a multiple independent PKG environment

In 2005, Lee et al. proposed an ID-based 2-party key agreement protocol between users whose private keys were issued by independent PKGs that do not share any system parameters. This work was the first kind that assumes completely independent multiple PKG environment. However, Lee et al. protocol has a flaw that allows attackers to impersonate others without knowing their private keys. In this paper, we propose a modification to the protocol of Lee et al. that prevents impersonation attacks. We also show a simple technique that can improve the efficiency of tripartite key agreement protocol of Lee et al. We also provide analysis of the security and efficiency of the proposed protocols.

Identity-Based key agreement protocols in a multiple PKG environment

To date, most identity-based key agreement protocols are based on a single PKG (Private Key Generator) environment. In 2002, Chen and Kudla proposed an identity-based key agreement protocol for a multiple PKG environment, where each PKG shares identical system parameters but possesses a distinct master key. However, it is more realistic to assume that each PKG uses different system parameters. In this paper, we propose a new two party key agreement protocol between users belonging to different PKGs that do not share system parameters. We also extend this protocol to a tripartite key agreement protocol. Our two party protocol requires the same amount of pairing computation as Smarts protocol for a single PKG environment and provides PKG forward secrecy. We show that the proposed key agreement protocols satisfy every security requirements of key agreement protocols.

PVR: a novel PVR scheme for content protection

Personal Video Recorders (PVR) are attractive to users because they enables us to watch content without facing time-restrictions. On the other hand, enterprises want to store content safely by using a proper encryption method to prevent a loss of their profits due to the leakage of content through PVR. Thus, it is necessary for enterprises to apply a method that effectively hinders the leakage of content while guaranteeing a certain level of QoS (Quality of Service). In this paper, we proposed a secure PVR method which uses a chipset-pairing, a form of advanced CAS. The proposed scheme has its merit in the fact that it can be directly usable for systems which use a chipset-pairing. Also, it generates a reasonable overhead to users and is effective to the leakage of content.

ID-based key management scheme using threshold decryption for OPMD environment

In this paper, we propose a key management scheme to protect contents in OPMD (One Person Multi Device) environment where a single user has multiple consumer devices. The proposed scheme using IBTD, a key management scheme that uses a user ID as a public key and the threshold decryption scheme that decrypts secret shares only if n the number of secret public values created by a contents server is more than t. Our proposed scheme enables users in OPMD environment to conveniently and easily use their contents through any of their multiple devices, and allows a contents server can manage keys efficiently in the user-centric key management way rather than in the device-centric key management way.

Key management scheme using secret sharing for multi-device based DRM

In this paper, we propose a key management scheme in DRM which supports multi devices by using a secret sharing. The proposed scheme enables playing contents on registered devices only, and additional overheads are not occurring even if the number of registered devices are increased. We measured the overheads occurred by the proposed scheme through a prototype implementation, and showed that the scheme is applicable to consumer devices.

Key Generation and Management Scheme for Efficient Interoperability among Different Downloadable Conditional Access Systems

CAS (Conditional Access System) is a content protection solution that restricts access to the system according to user`s standing and only authorized users can access the content in a pay-TV system. DCAS (Downloadable Conditional Access System) can download CAS client which is a software implemented via network. In recent years, research and development has been carried out on DCAS to solve the problems of compatibility among heterogeneous devices and internetworking with other services. In this paper, we propose key generation and management scheme for efficient interoperability among different DCASs based on PBC (Pairing Based Cryptography).

Efficient SVC encryption scheme in CAS for supporting heterogeneous devices

CAS used in IPTV and DTV was designed to transfer a single content through a single stream, but combined with SVC, it can be improved to support diverse video applications through a single streaming. For the environment, it is necessary to put efficiency in priority and to apply hierarchical management scheme in order to provide charging policy by each service class. In this paper, we investigated the issues that could occur as SVC was applied to CAS, and proposed SVC encryption scheme in the CAS environment. The proposed schemes safety was based on the safety of the existing CAS and one-way hash function, and the scheme has an advantage of applying to the existing CAS with relatively small overheads.

Key Distribution Scheme for Supporting Multiple Set-Top Box in Chipset Pairing Conditional Access System

In this paper, we propose a key distribution scheme for flexible chipset pairing conditional access system. Chipset pairing conditional access system is the implementation of CA (Conditional Access) module by using both embedded secure chip in a Set-Top Box(STB) and smartcard, and the secure chip embedded in a STB forms a secure channel between the smartcard and the STB. In short, it is the system that a smartcard outputs encrypted CW (Control Word) to the STB, and the STB decrypts an encrypted CW by using the embedded secure chip. The drawback of this chipset pairing conditional access system is that one smartcard is able to be used for only one specified STB since it is the system using the STB bound to a smartcard. However, the key distribution scheme proposed in this paper overcomes a drawback of current chipset pairing conditional access system by using Chinese Remainder Theorem(CRT). To be specific, with this scheme, one smartcard can be used for multiple, not single, STBs, and applied to current chipset pairing without great changes.

User-oriented key management scheme for content protection in OPMD environment

In this paper, we propose a key management scheme for content protection in the OPMD (One Person Multi Device) environment where one user owns multiple devices. IBTD (ID-Based Threshold Decryption) was applied for the proposed scheme, and this uses the user IDs and the device IDs as their public key. It is the key management scheme that can decrypt the encrypted content only when more than t secret sharing values are combined among the n secret sharing values generated by the contents server. Our scheme enables the users to use their own contents anytime and anywhere on any device that they own. For the contents server, it enables an effective key management which is user-oriented, not device-oriented.