Hyun Sook Rhee

Improved searchable public key encryption with designated tester

Recently, Baek et al. proposed an efficient public key encryption scheme with keyword search based on the scheme of Boneh et al., However, the security model of Baek et al. seriously limits the ability of the adversary. In this paper, we enhance the security model of the public key encryption with keyword search to properly incorporate the ability of an adversary. We also construct a public key encryption scheme with keyword search secure in the enhanced security model.

A remote user authentication scheme without using smart cards

User authentication is one of the fundamental procedures to ensure secure communications over an insecure public network channel. Especially, due to tamper-resistance and convenience in managing a password file, various user authentication schemes using smart cards have been proposed. A smart card however far from ubiquitous because of the high cost of a smart card and the infrastructure requirements. In this paper, we study secure user authentication using only a common storage device such as a universal serial bus (USB) memory, instead of using smart cards. We first show that the existing schemes using smart cards cannot be immediately converted into schemes using a common storage device. We then propose a practical and secure user authentication scheme, capable of supporting the use of the common storage device, which retains all the advantages of schemes using smart cards.

Secure searchable public key encryption scheme against keyword guessing attacks

Byun et al. firstly proposed off-line keyword guessing (KG)attacks and proved that some searchable public key encryption (PEKS)schemes are insecure against these attacks. They supposed an open problem on how to construct PEKS schemes secure against keyword guessing attacks. In this letter, we answer this question affirmatively.

Efficient and Secure Communication between Set-Top Box and Smart Card in IPTV Broadcasting

To provide secure delivery of satellite data in IPTV systems, service providers charge subscribing fee by scrambling the program in conditional access system using control words. At the receiver end, smart card is used to decrypt the control words and transfer them back to set-top box to descramble the scrambled program. Therefore, secure communication between set-top box and smart card is closely related with the benefit of service providers and the legal rights of users. In this paper, we propose secure mutual authentication and key agreement protocol between set-top box and smart card in IPTV broadcasting. The proposed scheme is more efficient than any other previously proposed schemes by eliminating exponentiation operations which are time-consuming. Moreover, our scheme can prevent two common serious problems - smart card cloning and McCormac Hack problems - in IPTV broadcasting.

Fully collusion-resistant trace-and-revoke scheme in prime-order groups

A trace-and-revoke scheme is a type of broadcast encryption scheme for content protection on various platforms such as pay-per-view TV and DVD players. In 2006, Boneh and Waters (BW) presented a fully collusion-resistant trace-and-revoke scheme. However, a decisive drawback of their scheme is to re- quire composite-order groups. In this paper, we present a new trace-and-revoke scheme that works in prime-order groups. Our scheme is fully collusion-resistant and achieves ciphertexts and pri- vate keys of size 0(√N) for N users. For the same level of security, our scheme is better than the BW scheme in all aspects of efficiency. Some superior features include 8.5 times faster encryption, 12 times faster decryption, and 3.4 times shorter ciphertexts. To achieve our goal, we introduce a novel technique where, by using asymmetric bilinear maps in prime-order groups, the cancellation effect same as in composite-order groups can be obtained.

A Fingerprint-Based User Authentication Scheme Using Smart Cards in IPTV Environments

In IPTV environments, a user authentication is an important security primitive to check the validity of membership. Authentication schemes between a smart card and set-topbox(STB) for authenticating users have been proposed in IPTV environment. Since many contents contain classifiable elements such as violence, sex, coarse language, themes and drug use, we should classify contents with ages and restrict an access ability of a user according to users age. Specially, to protect young children from a misusage of harmfulness contents, the legal and technical efforts are also required in IPTV. In aspect to technical efforts, it is required to provide an access control according to the policy of content provider. In this paper we first propose a fingerprint-based user authentication scheme which checks the suitability of user to the policy of contents provider. Since our scheme additionally contains a pre-computation phase, the computation cost of the smart cards is very low. And, the proposed scheme can also solve vulnerabilities against security problems such as smart card cloning and McCormac Hack attack in IPTV environment.

Fingerprint-based access control using smart cards in IPTV

In internet protocol television (IPTV) environments, authentication should be implemented to provide the IPTV contents to those legitimate subscribers. After successful authentication, a legitimate subscriber is unconditionally granted access to the contents. However, each content might have its own policy that restricts access according to subscriber’s attribute such as age. Authentication only is not sufficient to realize access control embracing diverse policies depending on contents. In this paper, we propose a novel fingerprint-based scheme that enables fine-grained access control according to the policies of contents providers and subscriber’s attribute. The proposed scheme is robust against man-in-the-middle attacks, replay attacks, and impersonation attacks which are considered as common threats in IPTV environments. The scheme also prevents cloning and McCormac Hack problems, that are critical attacks specific to authentication using smart cards.