The Virtual Private Network (VPN) technology provides a way of protecting information being transmitted over unsecure network. VPN uses encryption to provide data confidentiality and data integrity but does not provide or enforce strong user authentication. This paper proposes a new symmetric encryption algorithm for special purpose VPN to secure the classified data. The proposed algorithm based non Feistel structure with well-designed substitution boxes (S-Box), permutation networks, and a serial-parallel construction functions, in addition to key derivation algorithm which used the input secret key to generate sub-keys input for proposed algorithm. The security analysis of the proposed was conducted and the National Institute of Standards and technology statistical tests have been applied to the output of the algorithm proving its secrecy and randomness properties. In  addition, the performance of the proposed algorithm has measured per the execution time comparing with the standard algorithm.