  A one-time pad (OTP) based cipher to insure both data protection and
integrity when mobile code arrives to a remote host is presented. Data
protection is required when a mobile agent could retrieve confidential
information that would be encrypted in untrusted nodes of the network; in this
case, information management could not rely on carrying an encryption key. Data
integrity is a prerequisite because mobile code must be protected against
malicious hosts that, by counterfeiting or removing collected data, could cover
information to the server that has sent the agent. The algorithm described in
this article seems to be simple enough, so as to be easily implemented. This
scheme is based on a non-interactive protocol and allows a remote host to
change its own data on-the-fly and, at the same time, protecting information
against handling by other hosts.
