Abstract. As a convenient and low-cost mobile communication technology, short messaging service (SMS) is experiencing rapid growth and our fmdings provide practical implications for promoting SMS based Virtual Private Network successfully. Secure communication is an important aspect of any networking environment and also is an especially significant challenge in data transmission, fund transfers, important messages sending, etc, especially in ecommerce. Achieving secure communications in networks has been one of the most important problems in the information technology. I designed and developed a VPN framework based on PKI, including Certification Authority, Asymmetric Cryptography Algorithms, using Short Message Service to transmit small data from one computer to another party through Internet or GSM network that can be used in some enterprise organizations like Newspaper corporations, AZAD University (Science & Research). This framework for effecting the secure message transmission to another system uses Smartcards or SAM modules for storing the keys to guarantee the security of the message transmission. In this paper, we study necessary and sufficient conditions for achieving secure communications and present a solution to this problem using Smartcard and GSM network as a transfer platform.