The authors discuss the design and implementation of the authentication system called SPLICE/AS in the WIDE (widely integrated distributed environment) Internet environment. SPLICE/AS is designed based on the public-key encryption, and the authentication scheme originally proposed by R. M. Needham and M. O. Schroeder (1978). In order to manage a large-scale network like WIDE Internet, the hierarchical domain-based management scheme is introduced. Currently, the prototype of SPLICE/AS is working on the 4.3 Berkeley UNIX system. To improve the reliability and robustness of SPLICE/AS, the authors are modifying SPLICE/AS and developing a new protocol for database propagation which is discussed.