We propose a system architecture for mobile agents to improve their security in the environments of insecure networks and non-sophisticated terminals such as PDAs. As mobile agents freely migrate onto their favorite terminals through insecure networks or terminals, it is not appropriate for them to store some secret information for authentication and encryption/decryption. We introduce one and more secure nodes(OASIS NODE) for securely generating and verifying authentication codes. The each agent’s data are encrypted by a pseudo-chaos cipher mechanism which doesn’t need any floating processing co-processor. We’ve constructed a prototype system on a Java mobile agent framework, “Bee-gent" which implements the proposed authentication and cipher mechanisms, and evaluated their performances and their applicability to business fields such as an auction system by mobile agents.