We show a chosen plaintext attack against the RPC incremental unforgeable encryption scheme. The attack can forge a valid ciphertext efficiently. When Applying to 128-bit block RPC scheme, by the concept of birthday paradox, a forgery ciphertext can be gotten after 224 queries with probability larger than 1/2.

Asymmetric watermarking schemes have been widely discussed recently. Transformed-key asymmetric watermarking (TKAW) system is one of the schemes, which was proposed by Choi et al. This letter discusses the weaknesses of TKAW. In TKAW, the inner product of the received signal and public key almost equals to zero. As a result, it cannot resist projection attack. To prove this point, we will demonstrate how to find the most relevant unwatermarked signal y/spl tilde/ for a given watermark embedded signal y and prove that /spl par/y-y/spl par//spl les/|/spl alpha/|, where /spl alpha/ is a constant adjusted to a value that makes the watermark imperceptible. Moreover, we also find that the feature y-y/spl tilde/, a predicted watermark of a stego image, can be copied from a stego image to another image, which means that the TKAW system cannot resist copy attack either.

A distributed system is a collection of processor-memory pairs connected by communication links. The reliability of a distributed system can be expressed using the distributed program reliability, and distributed system reliability analysis. The computing reliability of a distributed system is an NP-hard problem. The distribution of programs & data-files can affect the system reliability. The reliability-oriented task assignment problem, which is NP-hard, is to find a task distribution such that the program reliability or system reliability is maximized. For example, efficient allocation of channels to the different cells can greatly improve the overall network throughput, in terms of the number of calls successfully supported. This paper presents a genetic algorithm-based reliability-oriented task assignment methodology (GAROTA) for computing the k/spl tilde/-DTA reliability problem. The proposed algorithm uses a genetic algorithm to select a program & file assignment set that is maximal, or nearly maximal, with respect to system reliability. Our numerical results show that the proposed algorithm may obtain the exact solution in most cases, and the computation time seems to be significantly shorter than that needed for the exhaustive method. When the proposed method fails to give an exact solution, the deviation from the exact solution is very small. The technique presented in this paper would be helpful for readers to understand the correlation between task assignment reliability, and distributed system topology.

This paper proposes an efficient method to implement RSA decryption algorithm. RSA cryptosystem is the most attractive and popular security technique for many applications, such as electronic commerce and secure Internet access. It has to perform modular exponentiation with large exponent and modulus for security consideration. The RSA cryptosystem takes great computational cost. In many RSA applications, user uses a small public key to speed up the encryption operation. However, the decryption operation has to take more computational cost to perform modular exponentiation by this case. This paper proposes an efficient decryption method not only based on Chinese remainder theorem (CRT) but also the strong prime of RSA criterion. The proposed decryption method only takes 10% computational costs of the traditional decryption method. It also reduces 66% computational costs than that of decryption methods based on CRT only. In a word, the speed of our proposed method is almost 2.9 times faster than the decryption method based on CRT only. The proposed method enhances the performance of the RSA decryption operation.

Information technologies have ushered in a new era for computer-related communications. Use of the Internet for commercial applications and resource sharing has accelerated in recent years as well. Owing to such developments, computer security has become a critical issue nowadays. In some applications, a critical message can be divided into pieces and allocated at several different sites over the Internet for security access concern. To access such an important message, one must access the divided pieces from different sites to reconstruct the message. In this paper, we propose model calculations to evaluate the probability of secret reconstruction and a weighted share assignment algorithm for assigning shares on hosts in such a way that the probability to be able to reconstruct the secret becomes the highest. Examples are presented to illustrate the feasibility of the proposed approach.

The use of the Internet for various business applications and resource sharing has grown tremendously over the last few years. In some applications, an important document may be required to be divided into pieces and be allocated in different locations over the Internet for security access concerns. For example, an important map that can be used to access a military base, an important key that can be used to give a military order or command. To access such an important document, one must reconstruct the divided pieces from different locations. In this paper, a probability model for reconstructing the secret sharing under the Internet is proposed. Also, how to assign the divided shares into different locations is studied. Particularly, algorithms to perform share assignment and to reconstruct the divided pieces into the original secret are proposed.

Data protection in computer systems is a rather complex problem. Data has to be protected while it is in memory, during communication and while it is stored on mass storage devices. During computation the central processor executes instructions and operates on data that are in readable form. The problem of operating on encrypted data was first considered by Rivest et al [4]. However, notrivial privacy homomorphisms do not exist. Thus it seems that isolation of users is the only alternative if security and privacy is to be achieved. However, in practice isolation is difficult to enforce. Worse, when user to user communication is allowed, more serious loopholes develop. Even though the problems of protection in Operating Systems in general are difficult, one does not have to settle for no security. Encryption allows the protection of data even when good security measures are lacking in an Operating System. In fact it is possible to design operating systems with improved protection using encryption [3]. In this paper we shall consider the problems of encrypted relational datsbases and show that it is possible under some circumstances to perform relational operations without decrypting an entire record.