It has been pointed out that in a ubiquitous environment, ensuring security will be extremely important as great many devices will be connected to the network in an open environment. However, most of devices that makes up a ubiquitous environment are embedded-type and compact, and lack computing resources. In addition to this, as the users are general users, there is rather strong demand for responsiveness, etc. Currently, Public Key Infrastructure (PKI) is available to provide security, but security systems that deploy this technology have some problems, such as large implementation size and long response time. To solve these problems, this research firstly downsized the X509 certification form, etc. and conducted research and development on electronic certification forms for embedded systems. Secondly, we conducted research to speed up public key encryption authentication deploying PKI by introducing ad hoc algorithms, etc.