Iuon-Chang Lin

Reversible Watermarking: Current Status and Key Issues

Over the past few years a number of research papers about reversible watermarks has been produced. Reversible watermarking is a novel category of watermarking schemes. It not only can strengthen the ownership of the original media but also can completely recover the original media from the watermarked media. This feature is suitable for some important media, such as medical and military images, because these kinds of media do not allow any losses. The aim of this paper is to define the purpose of reversible watermarking, reflecting recent progress, and provide some research issues for the future.

A new remote user authentication scheme for multi-server architecture

Abstract Remote user authentication is used to validate the legitimacy of a remote login user. Conventional user authentication schemes are suited to solve the privacy and security problems for the single client/server architecture environment. However, the use of computer networks and information technology has grown spectacularly. More and more network architectures are used in multi-server environments. In this paper, we propose a new remote user authentication scheme. The scheme can be used in multi-server environments. In our scheme, the system does not need to maintain any verification table, and the users who have registered in the servers do not need to remember different login passwords for various servers. In addition, our scheme can also withstand replay and modification attacks. Furthermore, it allows users to choose their passwords freely, and a user can be removed from the system easily when the subscription expires.

A SECURE NONREPUDIABLE THRESHOLD PROXY SIGNATURE SCHEME WITH KNOWN SIGNERS

In the (t;n) proxy signature scheme, the signature, originally signed by a signer, can be signed by t or more proxy signers out of a proxy group of n members. Recently, an efficient nonrepudiable threshold proxy signature scheme with known signers was proposed by H.-M. Sun. Suns scheme has two advantages. One is nonrepudiation. The proxy group cannot deny that having signed the proxy signature. Any verifier can identify the proxy group as a real signer. The other is identifiable signers. The verifier is able to identify the actual signers in the proxy group. Also, the signers cannot deny that having generated the proxy signature. In this article, we present a cryptanalysis of the Suns scheme. Further, we propose a secure, nonrepudiable and known signers threshold proxy signature scheme which remedies the weakness of the Suns scheme.

A practical (t, n) threshold proxy signature scheme based on the RSA cryptosystem

In a (t, n) threshold proxy signature scheme, the original signer delegates the power of signing messages to a designated proxy group of n members. Any t or more proxy signers of the group can cooperatively issue a proxy signature on behalf of the original signer, but (t - 1) or less proxy signers cannot. Previously, all of the proposed threshold proxy signature schemes have been based on the discrete logarithm problem and do not satisfy all proxy requirements. In this paper, we propose a practical, efficient, and secure (t, n) threshold proxy signature scheme based on the RSA cryptosystem. Our scheme satisfies all proxy requirements and uses only a simple Lagrange formula to share the proxy signature key. Furthermore, our scheme requires only 5 percent of the computational overhead and 8 percent of the communicational overhead required in Kims scheme.

A new steganographic method for color and grayscale image hiding

In this paper, we present a steganographic method for embedding a color or a grayscale image in a true color image. Three types of secret images can be carried by the proposed method: hiding a color secret image, hiding a palette-based 256-color secret image, and hiding a grayscale image in a true color image. Secret data are protected by the conventional crypto system DES. We compare the image quality and hiding capacity of the proposed method with those of the scheme in Lin et al.s scheme. According to the experimental results, the image quality of the proposed method is better than that of the Lin et al.s scheme. In addition, annotation data can be hidden with the secret image in the host image. The hiding capacity of the proposed method is greater than that of other compared schemes. The experimental results show that the proposed method is a secure steganographic method that provides high hiding capacity and good image quality.

Hiding data in spatial domain images with distortion tolerance

Data hiding is a technique that is used to embed secret information into a cover media. It has been widely used in protecting copyright and transmitting sensitive data over an insecure channel. Conventional data hiding schemes only focus on how to reduce the distortion when sensitive data is embedded into the cover image. However, the transmitted images may be compressed or occur transmitting errors. If such errors occur, the receiver cannot extract the correct information from the stego-image. In this paper, we proposed a novel hiding data scheme with distortion tolerance. The proposed scheme not only can prevent the quality of the processed image from being seriously degraded, but also can simultaneously achieve distortion tolerance. Experimental results show that the proposed scheme indeed can obtain a good image quality and is superior to the other schemes in terms of its distortion tolerance.

A simple micro-payment scheme

Abstract The micro-payment system is an important technique in electronic commerce. The high-value payment system is not suitable for a micro-payment system because the requirements are different. To meet sufficient security for all participants in electronic commerce, a micro-payment system makes it possible to make small payment through electronic communication networks. In this paper, we propose a simple and secure micro-payment system which can be used for purchasing information goods on the network. The new micro-payment system is developed using a tamper-resistant device (i.e., smart card), an efficient Message Authentication Code (MAC) technique, and the concept of overall network security. In our proposed scheme, we achieve the authentication of the legal users, protection of the integrity of transaction messages, and prevention of duplicate spending. This new micro-payment system is a simple, efficient and economical system.

A new key assignment scheme for enforcing complicated access control policies in hierarchy

In a traditional key assignment scheme, an access control policy is used to solve the access control problem in a hierarchy. A higher security class can access lower security classes, but the opposite is not allowed. However, in some cases, this can be troublesome because of the lack of flexibility. In this paper, we shall propose a secure key assignment scheme which can be performed not only in a hierarchy but also in more complicated policies with anti-symmetrical and transitive exceptions.

Adding timestamps to the secure electronic auction protocol

Recently, Subramanian proposed a secure electronic auction protocol. It was claimed that the auction protocol ensured anonymity, security, privacy, atomicity, and low overhead. However, the sensitive information of payment, such as credit card number, can be revealed by the auctioneer. The bid can be forged by a malicious auctioneer. Also, the situation of two or more bidders who offered the same price was not resolved efficiently. In this paper, we will improve the robustness of this electronic auction protocol.

Efficient access control and key management schemes for mobile agents

Abstract The mobile agent is a promising trend of technology. It is designed for roaming around the Internet and to achieve the goal of autonomy. However, the Internet is an open and, in many cases, a hostile environment. Thus, how to enable the mobile agent to travel through the Internet in safety is an important issue. Recently, Volker and Mehrdad have proposed a structure that supports key management and access control for mobile agent. However, a large amount of storage for storing the secret keys is required in their scheme. In this paper, we will improve their structure and present two novel methods for key management and access control in a hierarchy. According to our security and performance analysis, our proposed scheme is more suitable for mobile agent environments.