8. The method of claim 7 , wherein determining a security level of the pseudo message based on a distance from a relationship edge associated with the rule in the recipient Ontology to a root concept node in the recipient Ontology comprises determining the security level according to: 
 secu=α·dis, where: secu is the security level; α is a weighting constant such that 1/dis MAX >α>0; dis MAX is the maximum dis in the recipient Ontology; and dis is a number of concept nodes from the root node to a concept node connected to the relationship edge that is farthest from the root node.
7. The method of claim 6 , further comprising determining a security level of the pseudo message based on a distance from a relationship edge associated with the rule in the recipient Ontology to a root node in the recipient Ontology.