As an open source project, Open Simple Secure Transaction (OpenSST) protocol aims to be a secure and transactionoriented protocol for the unsecured network. At present a prototypes has been implemented. In this paper, we give firstly an overview of OpenSST, and then we describe the key store and authentication mechanism of the prototype, as well as make an analysis on its security. Then we introduce a security-enhanced model based on this prototype, which integrates Smart Card into the OpenSST protocol. This model demonstrates how to use Smart Card to improve the public key authentication process in a secure network protocol. KEYWORDS OpenSST, Smart Card, Key store, Authentication, Public Key, Private Key