Chen-Yu Lee

Comments on Saeednia's improved scheme for the hill cipher

Abstract In 2000, Saeednia proposed a new scheme to make the Hill cipher secure. The author makes use of permutations of columns and rows of a matrix to get a different key for encrypting each message. This paper shows that the cipher key Ht can be obtained by parameter u. Besides, the Saeednias scheme costs a lot of time in matrix computation. To overcome the drawbacks of Saeednias scheme, a more secure cryptosystem with a one‐way hash function is proposed.

A detection scheme for flooding attack on application layer based on semantic concept

With the development of the Internet, application programs on the web page become widespread. Information appearing on the web page has evolved from static presentation to dynamic presentation and even being interactive with the users. Some malicious users employ malicious browsing behaviors, such as flooding attack, to cause waste of resources and bandwidth of the host for the web page. Since the advent of cloud computing technology, flooding attack on the application layer no longer has the ability to cause complete denial of service to a Web server. But resources, such as bandwidth, CPU time, and memory, on the clouds mean cost, and any waste of the resource will generate extra and unnecessary cost. Therefore, in this paper we analyze native modules or components of the PHP dynamic pages and find the amount of system resources consumed by parts of the native module or the whole module. From above analysis, we propose a method based on semantic concept to formulate rules to identify malicious browsing behaviors in order to improve performance of Web services and to slice the cost.

Generalized secure hash algorithm: SHA-X

This paper defines a generalized SHA algorithm based on the SHA family rules. The proposed algorithm accepts arbitrary length message as input to generate message digest with the required length. It contains the initial values, constant values, padding, parsing, as well as the generalized main body. Further, the proposed algorithm solves the Length-of-the-Hash-Value (LHV) problem that occurs when SHA-r cannot be expressed as r = mn uniquely.

Modified Autonomous Key Management Scheme with Reduced Communication/Computation Costs in MANET

The growing applications of Mobile Ad hoc Network (MANET) has made the security issue increasingly more important. B. Zhu et al. proposes a key management scheme using Shamir’s secret sharing scheme to construct an Autonomous Key Management (AKM)hierarchy structure. However, Shamir’s secret sharing in AKM to control key hierarchy needs larger message transmission costs. In this paper, we modify the secret sharing scheme and apply it to AKM for reducing communication and computation cost.

Investigations of Factors Affecting the Genetic Algorithm for Shortest Driving Time

In this paper we investigate the influences on the genetic algorithm for the shortest driving time problem due to factors such as nodes on a map, the population size, the mutation rate, the crossover rate, and the converging rate. When the nodes on the map increase, more execution time is needed and much difference between the approximate solution and the exact solution appear on running genetic algorithms. Also, from the view point of the population initialization, restart type and reback type affect the precision of approximate solutions and the execution time. The characteristics of the factors we find in the paper provide us insight how to improve the genetic algorithm for the shortest driving time problem.

Visible Watermarking Based on Multi-parameters Adjustable Gamma Correction

With the progress of information technology, digital data is a major trend of business communication today. Therefore, copyright protection of digital data has been an important research issue of information security. In the paper, we proposed an improved visible watermark scheme using multi-parameters adjustable Gamma Correction to reduce the distortion, which can increase color saturation. Our experiments showed that the PSNRs of the stego images with watermark embedded were up to 54.50 dB and 58.66 dB.

Unseen Visible Watermarking for Gray Level Images Based on Gamma Correction

In this paper, we proposed a novel watermarking technology with the properties that from visible watermarking and invisible watermarking. In the common situation our approach can be used to transmit the multimedia files, according to the gamma correction, the watermark can be revealed. Our proposed method has a unique feature that we can obtain a watermarked-image similar to the original image after embedding watermarks. The naked eye hardly realized the watermarks, but after adjusting the viewing angle, it then demonstrated the embedded watermarks. We embed the unseen visible watermarks by adjusting degree of saturation and value of HSV model in the color space. The experiment result shows that the PSNR values of the watermarked images are more than 45 dB, sometimes even as high as 55 dB.

Keyed/Unkeyed SHA-2

Abstract In FIPS 180–2, NIST published SHA-2 as a new version of secure hash algorithm. SHA-2 offers four secure hash algorithms including SHA-1, SHA-256, SHA-384, and SHA-512. In other words, SHA-2 may have outputs 160, 256, 384, or 512 bits of message digest. However, SHA-2 algorithm uses fixed and predefined parameters in execution. It may be vulnerable to attacks. In this paper, we propose the Keyed/Unkeyed SHA-2 for security improvement.

Finding Near-Optimum Message Scheduling Settings for SHA-256 Variants Using Genetic Algorithms

One-way hash functions play an important role in modern cryptography. Matusiewicz et al. proved that the message scheduling is essential for the security of SHA- 256 by showing that it is possible to find collisions with complexity 264 hash operations for a variant without it. In this article, we first proposed the conjecture that message scheduling of SHA algorithm has higher security complexity (or fitness value in Genetic algorithm) if each message word (Wt) involves more message blocks (Mi) in each round. We found some evidence supports the conjecture. Consider the security of SHA-0 and SHA-1. Since Chabaud and Joux shown that SHA-1 is more secure than SHA-0. Further, Wang found collisions in full SHA-0 and SHA-1 hash operations with complexities less than 239 and 269, respectively. We found it is consistent from the viewpoint of message blocks (terms) involved in each message word. It clearly shown that the number of terms involved in SHA-1 is more than that in SHA-0, taking W27 as an example, 14 and 6, respectively. Based on the conjecture we proposed a new view of complexity for SHA- 256-XOR functions, a variant of SHA-256, by counting the terms involved in each equation, instead of analyzing the probability of finding collisions within SHA-256-XOR hash function. Our experiments shown that the parameter set in each equation of message schedule is crucial to security fitness. We applied genetic algorithms to find the near-optimal message schedule parameter sets that enhance the complexity 4 times for SHA-1 and 1.5 times for SHA-256-XOR, respectively, when compared to original SHA- 1 and SHA-256-XOR functions. The analysis would be interesting for designers on the security of modular-addition-free hash function which is good for hardware implementation with lower gate count. And the found message schedule parameter sets would be a good reference for further improvement of SHA functions.

A Software Protection System for Internet Commerce

Copyright protection of software program is crucial for the prosperity of software market. In this paper, we propose a dual software protection scheme. After purchasing a program from merchant, a buyer can exactly install it once. If the buyer redistributed a copy of the program, it could not be installed. Further, if the buyer could break the protection method and redistributed a copy of program, the merchant would be able to identify the traitor.