To solve the distributed hierarchical network security problems, a distributed simple strictly hierarchical (DSSH) PKI trust model is presented. This model provides effective network security services such as authentication, access control, integrity, confidentiality, non-repudiation and so on. On the basis of the trust model, the concept of the issue-seal certification is presented and established to ensure the security of the seal file in the CA domain. The system implements the digital signature and verification of the electronic documents by the electronic seal. The key, which encrypts and decrypts the electronic documents, is protected by the encryption certification. Finally, the system implements the management of printing seal files abilities through the authority server.