SCADA systems gather data from remote sensors and transfer that data to a central controller for analysis. As this data  is frequently of a confidential nature, securing that data is an important challenge. We can take two perspectives when examining Wireless Sensor Network (WSN) security - the security of the data in transit and the security of the network itself.

The data transferred from a WSN has to be protected from unauthorised viewing, unauthorised tampering or both. Cryptographic systems prevents viewing and tampering while Digital Signatures ensure data integrity. Digital signatures can ensure that data is from authorised senders and can also ensure that data arrives untampered. Quality of Service (QoS) metrics can also be met using digital signatures by ensuring that data isn't duplicated maliciously or otherwise. Encryption provides further protection by guarding against eavesdropping i.e. ensuring that the data cannot be viewed while it's in transit.

From the point of view of Network Security, device identities must be provable and data transfer from one mote to another or from a mote to a SCADA system must be authorised. Attacks should be logged and key management should be feasible.  This latter point is critical given the constrained nature of a typical sensor mote in terms of processing power and memory. For this reason non-traditional cryptographic techniques such as Elliptic Curve Cryptography (ECC) and Identity Based Encryption (IBE) should be considered. The former is an option that has been used by TinyOS and Java-based sensor motes.

SCADA-based WSNs typically consist of many motes with, as noted above, severe resource constraints. Given that SCADA systems have physical access to devices, the use of cryptographic protections might not be enough as attacks on these systems could be catastrophic in nature. It is argued  (See http://www.mdpi.com/1424-8220/9/11/9380/pdf) that a reputation system is required. Within this system only trusted data is transferred from sensor to server while the server provides the reputation to the sensor .

Given the critical nature of SCADA systems for many industries and utilities, the data that flows through the system needs to be secure. The introduction of WSNs into a SCADA system can damage that security unless appropriate security provisions are made be they digital signing, cryptography or a reputation-based system.