Given the current security situation on the Internet, it is important to determine the trust of the communication routes between a client and server. However, such determination can only be established by end terminals such as clients and servers, not by intermediate routers or network providers so far. Revelations regarding PRISM and other programs highlight the importance of this issue. In this paper, a method to identify the trust level of a route between a client and a server is proposed that uses packet authentication, Probabilistic Packet Marking (PPM), and knowledge bases maintained by trusted third parties. A prototype system of the proposed method was developed and evaluated, prove its feasibility. To the best of our knowledge, the proposed method is the first for identifying the trust level of a route based on information obtained from intermediate routers or Autonomous Systems (ASs).