A Free-Roaming Mobile Agent Security Protocol against Colluded Truncation Attack without trusted third party

To secure the free-roaming mobile agent´s data protection, especially to resist the colluded truncation attack, we proposed a new security mechanism which can not only satisfy security demands, but can also solve the bottleneck problem caused by trusted third party, we call the new mechanism ISTCM. In ISTCM, task sponsor first chooses a certain number of hosts as partners at random. When agent reaches a host, the host consults the partners of encryption key. Data generated by the host is encrypted into a divisible whole for protection. At the same time, the host sends its identity information to partners according to threshold scheme. When agent comes back to task sponsor, it will compare path from passing data with path from the partners to find out if there exists attack. Analysis shows the mechanism can defend the colluded truncation attack effectively.