Information security is a key requirement in emerging networked scenarios, which typically involve a large variety of heterogeneous, often resource-constrained devices. Providing security to this emerging class of distributed applications raises a number of new challenges. This paper discusses such challenges with respect to two key security services, namely Public Key certification and digital timestamping, and presents a multi-tier architecture which combines a hardware-accelerated back-end and a Web Services based web tier to for achieving interoperability while boosting performance. The paper describes the organization of the multi-tier architecture, provides a detailed description of individual components, and presents the results of a thorough experimental campaign