WirelessHART: secure by design

23 October 2016

Data security is critical to the successful deployment of field instruments in plant applications. Suzanne Gill asked a variety of automation vendors for their views on WirelessHART security and their own strategies to ensure network security.

It is obvious that thoughts about data security will be high in the mind of any engineer planning to install a wireless network. According to Kurt Polzer, senior consultant solutions & training for Siemens Industry Sector, there are two key areas that need to be considered – WirelessHART and the connection from the gateway to a system. He said: “By default WirelessHART supports integrated security mechanisms such as a strong 128-bit AES-Industry standard encryption and usage of a message integrity (MIC) code. Communication between the process control system and the WirelessHART gateway is based on three IP based protocols – HTTPS for configuration of the gateway with a per-definition integrated security, HART-IP for parameterisation of the WirelessHART devices and Modbus-TCP to transmit the process values to the controller. 

“The security of HART-IP and Modbus-TCP needs to be considered and assured by the operator,” continues Polzer. With its industrial security offering, Siemens provides the technology, systems and products needed to achieve the required security level for both local and remote connections. For example, in the form of Virtual Private Networks (VPN), Industrial Security provides secured communication from the WirelessHART device to the user or system.

From the beginning
Eric Braun, wireless security engineering manager at Emerson Process Management, says that WirelessHART security is enabled from the very beginning - as soon as an instrument is taken out of its box. ‘All layers  are protected from the host system, via the gateway, to field devices. All messages are encrypted and will not be readable, which protects the data,”  he said.

Braun goes on to highlight a key security feature of the WirelessHART network. “Each device on the network is authenticated with a join key. This means that unintended devices are kept off the network and only authorised devices are allowed to join.” This join key can be unique for each device or can be common for the entire WirelessHART network. “Unique join keys are never revealed to the user. Join keys are given to each device via a wired HART connection meaning that encryption keys are never transmitted wirelessly in clear text,” he said.     

Having the ability to send a secure message is an important part of a WirelessHART network. Braun explains: “Devices send encrypted messages to the gateway and multiple keys are used during communication. The session key and a network key are used to ensure that the message transfer process is accurate and secure. Message encryption prevents outsiders from reading an intercepted message, preventing false messages from being sent.

“Additionally, at the Gateway, many secure Ethernet protocols are supported, allowing users to select from a set of industry standard protocols,” said Braun. Because of the quantity of protocols supported, host integration is simple. By default, only secure protocols are enabled, which means that unless the user intentionally makes protocol changes, all Ethernet communication from the Gateway will be encrypted. This allows users to comply with their own security practices.”

Not an issue
Diederick Mols, global market development leader wireless at Honeywell, says that security should not be an issue with WirelessHART  networks. “The FieldComm Group (previously HART Foundation) spent a great deal of time ensuring the highest level of security at all times,” he said. The security protocol is very strict and once a device is on the network it will continuously rotate keys.  “There are now billions of WirelessHART operating hours with no breaches of security yet being recorded,” said Mols.  “Indeed, one of the benefits of a wireless network is that it can ensure network integrity. If there is a communication failure, a wireless network will issue an alarm, which is not possible in the event of a corrupted wired network.”

Honeywell has reported an increased uptake in interest in wireless networks which is confirmed by ISA reports that quote figures of  around 12% growth in wireless year-on-year. Honeywell remains protocol agnostic with its OneWireless network solution which is able to communicate with all wireless communication networks. 

“The next step for Honeywell will be the  introduction of a universal wireless IO which will form part of the next Experion release 500,” concludes Mols. This will allow access points to talk natively with all wireless devices without the need for any translation.  Customers want protocol agnostic solutions and want to be able to integrate any make of transmitter into their network. We will make this possible early next year.” 

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