Chi-Sung Laih

New Colored Visual Secret Sharing Schemes

Visual secretsharing (VSS) schemes are used to protect the visual secret bysending n transparencies to different participantsso that k-1 or fewer of them have no informationabout the original image, but the image can be seen by stackingk or more transparencies. However, the revealedsecret image of a conventional VSS scheme is just black and white.The colored k out of n VSS scheme sharinga colored image is first introduced by Verheul and Van Tilborg[1]. In this paper, a new construction for the colored VSS schemeis proposed. This scheme can be easily implemented on basis ofa black & white VSS scheme and get much better block lengththan the Verheul-Van Tilborg scheme.

On key distribution management for conditional access system on pay-TV system

A conditional access system (CAS) is essential in a pay-TV system to charge the subscriber the subscription fee, and key management is also important. Various levels of key hierarchy for a CAS are discussed and two methods of grouping the subscribers to reduce the complexity of key distributions are presented. Based on the proposed two grouping methods we proposed a simple and a complete scheme with four-levels of key hierarchy for the key distribution management CAS of the pay-TV system. We also analyze the performance of the proposed complete scheme. It is shown that our system is efficient and suitable for a pay-TV system which provides both pay per channel (PPC) and pay per view (PPV) services. Besides, the proposed complete scheme is also a flexible one for dynamic management. Finally, it should be noted that, though our discussion are focused on pay-TV only, our schemes are also suitable for a digital broadcasting system (DBS).

Malicious web content detection by machine learning

The recent development of the dynamic HTML gives attackers a new and powerful technique to compromise computer systems. A malicious dynamic HTML code is usually embedded in a normal webpage. The malicious webpage infects the victim when a user browses it. Furthermore, such DHTML code can disguise itself easily through obfuscation or transformation, which makes the detection even harder. Anti-virus software packages commonly use signature-based approaches which might not be able to efficiently identify camouflaged malicious HTML codes. Therefore, our paper proposes a malicious web page detection using the technique of machine learning. Our study analyzes the characteristic of a malicious webpage systematically and presents important features for machine learning. Experimental results demonstrate that our method is resilient to code obfuscations and can correctly determine whether a webpage is malicious or not.

A Hop-Count Analysis Scheme for Avoiding Wormhole Attacks in MANET

MANET, due to the nature of wireless transmission, has more security issues compared to wired environments. A specific type of attack, the Wormhole attack does not require exploiting any nodes in the network and can interfere with the route establishment process. Instead of detecting wormholes from the role of administrators as in previous methods, we implement a new protocol, MHA, using a hop-count analysis from the viewpoint of users without any special environment assumptions. We also discuss previous works which require the role of administrator and their reliance on impractical assumptions, thus showing the advantages of MHA.

A new threshold scheme and its application in designing the conference key distribution cryptosystem

Abstract This paper presents a new threshold scheme, which is based on the definition of cross-product in an N -dimensional vector space. By employing this scheme, the single-system master key can be shared among multiple users. It provides a protection of property against problems such as abnegation incidents or betrayal incidents. This scheme can also be applied for designing conference key distribution systems.

Server-less RFID authentication and searching protocol with enhanced security

This paper focuses on two interesting radio-frequency identification (RFID) cryptographic protocols: the server-less RFID authentication protocol that allows readers to authenticate tags without the help of any online backend servers, and the RFID searching protocol in which the verifier explicitly specifies the target tag to be searched and authenticated. These two kinds of RFID protocols play important roles in many RFID applications; however, the existing protocols either had security weaknesses or exhibited poor efficiency. This paper shows the weaknesses, and then proposes our server-less RFID authentication protocol and RFID searching protocol. The proposed protocols greatly enhance the security using one more hashing. Copyright

ECC-based lightweight authentication protocol with untraceability for low-cost RFID

Due to the potential wide deployment of Radio Frequency Identification (RFID), the security of RFID systems has drawn extensive attention from both academia and industry, and the RFID authentication protocol is an important mechanism in the security of RFID systems. The desired security requirements of RFID authentication protocols include privacy, integrity, authentication, anonymity/untraceability, and even availability. To design an efficient protocol that satisfies all the requirements with limited resources is a challenge. This paper proposes a new RFID authentication protocol based on Error Correction Codes (ECC). The proposed scheme has excellent performance in terms of security, efficiency, servers maintenance, robustness, and cost. The tag only performs simple operations, such as random number generation and simple bitwise computations. The lightweight feature makes it attractive to those low-cost RFIDs that support only simple operations.

Merging: an efficient solution for a time-bound hierarchical key assignment scheme

Conventional hierarchical key assignment schemes have not been concerned with a practical situation: Users might be assigned to a class for only a period of time. When a user leaves a class, the keys of that class and all the descendent classes must be renewed. For applications where the privileges of users change frequently or where there are many users, the communication load for key redistributions is very large. Recently, Tzeng (2002) proposed a time-bound hierarchical key assignment scheme to address this issue. However, Tzengs scheme was very complex and suffered from a collusion attack. In this paper, we propose an efficient time-bound scheme based on a technique called merging. The idea behind merging is to consider primitive keys instead of hierarchies. It is conceptually like the compression used in source coding. Through this technique, it is feasible to combine multiple keys into an aggregate key. Thus, communication and storage requirements are greatly reduced. This technique can also be used for an alternative implementation of Akl-Taylors scheme. Moreover, it can be used to construct a systematic approach for adjusting hierarchies in Akl-Taylors scheme as well. Through the insights gained from these exercises, we may see that some problems that are usually addressed by the conventional key assignment schemes can be solved directly via merging, with better performance. Furthermore, if other suitable merging functions are found in the future, new secure hierarchical key assignment schemes and time-bound schemes is obtained accordingly.

Improved digital signature suitable for batch verification

In this paper, an improved digital signature is developed based on the famous Schnorr (1990) or Brickell-McCurley (1991) schemes. It is shown that both the new scheme and the previous two originals rely on the same security assumptions. The novel feature of this proposed signature is that it can be verified in a batch manner and the improved efficiency is approximately proportional to the number of signatures to be verified. >

Efficient Key Distribution for Access Control in Pay-TV Systems

The conditional access system (CAS) is an essential part of digital pay-TV systems for controlling access to the program services. Conventionally, due to the restrictions of bandwidth and computational capability, a CAS only supports period subscription services that are charged on a monthly basis. In this paper, based on the concept of hierarchical key assignment, we propose three key distribution schemes for the access control of pay-TV systems. With these schemes, a CAS can support more charging strategies for service providers, such as adopting a smaller charging unit and allowing a subscription of any subset of channels with little communication and computational overhead. In addition, the piracy management problem can also be dealt with easily.