Abstract
The phrase "Ubiquitous Computing" has become popular ever since Mark Weiser used it in an article. It is to realize a computerized environment in which small computers are embedded and cooperate with each other. This environment will support many activities of our daily life. In a Ubiquitous Computing environment, various devices will be connected to the network from houses and buildings. Therefore it is necessary to ensure network security and to protect private data from tapping, falsification and the disguising of identity by others. This study reviews the Ubiquitous Computing technologies in detail and outlines the design concept of the Stream Cipher Algorithm.