Research And Application Of SSL In Automatic Test System Based On LXI Bus

With the rapid development of computer technology and automation technology, great changes have taken place in testing field. The traditional instrument system with independent or local control is becoming more and more incommensurate, so the LXI bus standard based on network technology appeared. LXI is the development of mature Ethernet technology in test automation field. It incorporates the high performance of GPIB instrument, the small volume of VXI/PXI cassette instrument and the high-speed throughput of LAN. Meanwhile, instruments requirements such as the timing, trigger, cooling and electromagnetic compatibility are also taken into consideration. According to these advantages, LXI, based on Ethernet, is a new modularization structure platform standard of automatic test system. However, due to the openness of network, many security problems could threaten the safe use of automatic test system when test data is being transferred in the network.As a network data security communication protocol, SSL is widely used in the world. Based on the encryption techniques, it realizes the functions of identity authentication, data encryption, integrity check and digital signature. Therefore, the safety problems of network test data transfer can be well solved by using the SSL protocol in automatic test system.Based on the SSL protocol, an SSL secure proxy is designed by using the open source software packages OpenSSL in this thesis.This proxy is divided into SSL client proxy and SSL server proxy. These two proxies are placed in the joint of the intranet and extranet and construct a safe data transmission channel of C/S structure. In order to realize the identity authentication function between the SSL security proxies, a small CA system is also designed which can sign the x.509 digital certificate and provide identifying authentication certificate for communications. Althouth the use of encryption technology can guarantee the security of data transmission, it also reduces the system performance. Therefore, a method of dynamic encryption is proposed which can remarkably improve system performance by using different strategies of encryption for different importance of data.