Protecting mobile code

There are at least two major security challenges in mobile code distributed systems. First hosts have to be protected from potentially malicious actions of mobile code they are executing. Many techniques are known which address this problem. Second mobile agents themselves have to be protected against malicious hosts. Satisfactory ways to deal with the second problem are necessary features for many of the (security-sensitive) tasks mobile agent (MA) systems are envisioned for, e.g., in e-commerce applications where a shopping agent is sent out on the Internet, vendors have a high incentive in tampering with these agents. The key point is is that the originator of the agent needs to have sound guarantees that the results an agent brings back are correct. Why else should he send out the agent in the first place?