Mobile code based computing requires development of protection schemes that allow digital signature and encryption of data collected by the agents in untrusted hosts. These algorithms could not rely on carrying encryption keys if these keys could be stolen or used to counterfeit data by hostile hosts and agents. As a consequence, both information and keys must be protected in a way that only authorized hosts, that is the host that provides information and the server that has sent the mobile agent, could modify (by changing or removing) retrieved data. The data management model proposed in this work allows the information collected by the agents to be protected against handling by other hosts in the information network. It has been done by using standard public-key cryptography modified to support protection of data in distributed environments without requiring an interactive protocol with the host that has dropped the agent. Their significance stands on the fact that it is the first model that supports a full-featured protection of mobile agents allowing remote hosts to change its own information if required before agent returns to its originating server.