Creating confidential data via encryption is now a trivial task; however, managing the necessary public and private keys in a large organization is a serious challenge. Software agents can be an adaptive, responsive mechanism for managing client authentication and maintaining user credentials. By using a distributed community of software agents, we can match the growth in the software and hardware we seek to protect. Also, if these agents act collaboratively to distribute solutions to security violations, we can construct a rapid, scaleable defense mechanism. The prototype Phobos agent architecture offers such a solution to the authentication problem. It provides a number of security services with the goal of automating user authentication and trust management. In particular, the agents should handle all password, key, and certificate management. Phobos therefore provides a multiparty authentication service.