Supervisory Control and Data Acquisition (SCADA) systems are widely used in critical infrastructure sectors including power, gas, oil and water. Several malicious attacks aiming at SCADA systems have caused serious consequence in recent years. The communication in SCADA systems is particularly vulnerable to malicious attacks. In this paper, the authors put forward a Bump-In-The-Wire (BITW) solution which provides cryptographic protection for SCADA communication. Compared with existing solutions, their solution can achieve better performance in some key properties: integrity, availability, latency and hardware cost.