Cohesion is an important software attribute, and it is one of significant criteria for assessing object-oriented software quality. Although several metrics for measuring cohesion have been proposed, there is an aspect which has not been supported by those existing metrics, that is "cohesive-part size." This paper proposes a new metric focusing on "cohesive-part size," and evaluates it in both of qualitative and quantitative ways, with a mathematical framework and an experiment measuring some Java classes, respectively. Through those evaluations, the proposed metric is showed to be a reasonable metric, and not redundant one. It can collaborate with other existing metrics in measuring class cohesion, and will contribute to more accurate measurement.

In this paper we propose SAS-Coin, a very practical micro payment scheme based on a hash chain and a simple one time password authentication protocol called SAS. While it has many desirable features of a coin (anonymity etc.), it has no public key operations at any stage and has very little overheads. Moreover authentication is also available and a session key could be generated for encrypted information supply without any additional cost at all. Since there are no public key operations this is extremely useful for mobile telephone applications. This has sufficient security even for larger payments. Comparative analysis with some of the already proposed systems is also done.

SAS-2 is an alternative of a one-time password authentication protocol SAS, and is developed in order to reduce overhead due to the use of hash functions. The idea of both algorithms is sharing a similar secret number called the verifier that allows a client to be authenticated and that is changed for each new session. However, some of the combinations proposed in [1] to transmit the verifier may contain a security flaw, and the insecure combination results in vulnerability to impersonation attacks.

In the Internet and Mobile communication environment, authentication of the users is very important. Although at present password is extensively used for authentication, bare password transmission suffers from some inherent shortcomings. Several password-based authentication methods have been proposed to eliminate such shortcomings. Those proposed methods have relative demerits as well as merits. In this letter we propose a method where those demerits are eliminated. The prominent feature is security improvement apart from low processing, storage and transmission overheads compared to previous methods. This method can be used in several applications like remote login, encrypted and authenticated communication and electronic payment etc.

Properly representation of the complexity of class structure will be useful in object oriented software developments. Although some class complexity metrics have been proposed, they have ignored directions of coupling relationships among methods and attributes, such as whether a method writes data onto an attribute or reads data from the attribute. In this paper, we use a directed graph model to represent such coupling relationships. Based on the directed graph model, we propose a metric of class structural complexity. The proposed metric satisfies necessary conditions of complexity metric suggested by Briand and others. The following fact is showed by experimental data of Java classes. While the proposed metric follows a conventional metric, the proposed metric can capture an aspect of class structural complexity which is lost by the conventional one.

Larger object classes often become more costly classes in the maintenance phase of object-oriented software. Consequently class would have to be constructed in a medium or small size. In order to discuss such desirable size, this paper proposes a simple method for predictively discriminating costly classes in version-upgrades, using a class size metric, Stmts. Concretely, a threshold value of class size (in Stmts) is provided through empirical studies using many Java classes. The threshold value succeeded as a predictive discriminator for about 73% of the sample Java classes.