Agent integrity is one such area crucial to the success of agent technology. The integrity protection for agent code is relatively straightforward. A more complex code integrity scheme to handle code-on-demand is also proposed in Wang et al. (2002). Agent data, however, is dynamic in nature and will change as the agent roams from host to host. Despite the various attempts in the literature (Chionh, Guan, & Yang, 2001), there is no satisfactory solution to the problem so far. Some of the common weaknesses of the current schemes are vulnerabilities to revisit attack and illegal modification (deletion/insertion) of agent data.