Generalized Multi-Protocol Label Switching（GMPLS） is used as the control protocol for ASON

of which the routing part is mainly governed by the Open Shortest Path First（OSPF） protocol.In this paper

the hidden trouble in the encryption for OSPF protocol is analyzed and the existing encryption schemes improved.A new and safer scheme applicable to the routing technology in ASON is proposed.On the basis of the number-theoretic algorithm

the S-box is dynamically adjusted to prevent differential cryptanalysis.The encryption solution fulfills the confusion and diffusion principle.