Secret key encipherment is a basic technique for information security. The authors propose a new encipherment algorithm which is fast in software on 32-bit microprocessors. It is a 128-bit block encipherment algorithm and has fundamental security due to variable bit-rotations in the enciphering process. The algorithm is safe against trial-and-error key exhaustive attack and attacks utilizing the statistical properties of related plaintext and ciphertext pairs. The encryption speed is over 7 Mbps on a µP68030 microprocessor (25 MHz). This performance is about three or four times faster than that of FEAL-8. The algorithm will be effective for encryption in multimedia communication environments and as a hash function for message authentication, and digital signatures.

An abstract enciphering machine model (AEM model); an encipherment evaluation model considering the recent trends in computer architecture is proposed. With the advances in computer communication, network security is an important issue. Although there exist several encipherment method, there is no abstract measure for comparing encipherment algorithms. The authors implemented several encipherment algorithms is C and assembler with several programming techniques. Observing the improvements in various programming techniques, especially with RISC processors, it has lead us to believe that the amount of algorithm-specific improvement techniques is small. It is noted that there exists an abstract machine model which can predict encipherment algorithm performance without implementation. The authors discuss the parameter value in the AEM model for encipherment evaluation comparing the real observation with the predicted values. Also, the upperbound speed of ideal fast encipherment algorithms is discussed with the AEM model.

The use of computers with private networks has accelerated the electronic storage of business information in office systems. With the rapid progress in processing capability and small sizing of the computer world, private networks are going to be more intelligent. The utilization of shared information is a key issue in modern organizations, in order to increase the productivity of white-collar workers. In the CSCW research field, it is said that informal and unstructured information is important in group work contexts but difficult to locate in a large organization. Many researchers are paying particular attention to the importance of support systems for such information. These kinds of information are called Organizational memory or Group Memory. Our research focuses on knowledge propagation with private networks in the organization. This means emphasis on the process; with which organized information or the ability to use information is circulated throughout the organization. Knowledge propagation has three issues: knowledge transmission, destination locating and source locating. To cope with these issues we developed FISH, which stands for Flexible Information Sharing and Handling system. FISH was designed to provide cooperative information sharing in a group work context and to explore knowledge propagation. FISH stores fragmental information as cards with multiple keywords and content. This paper discusses a three-layered model that describes computer supported knowledge transmission. Based on this model, three issues are discussed regarding knowledge propagation. FISH and its two-year experiment are described and knowledge propagation is explored based on the results of this experiment.