Protocols

Communication Protocols

IEC-61850
IEC-61850 is an international standard for substation communications. IEC-61850 does not have a security function built in, but rather it uses SSL/TLS for confidentiality and authentication. IEC-61850 uses hash algorithms and public key cryptography making it a secure protocol.

Distributed Network Protocol Distributed Network Protocol (DNP) is a common communications protocol used between devices in an automation system. DNP can be over a serial communications line or as a layer 2 network protocol. DNP over serial, to be secure, needs a wrapper – a device that adds encryption and authentication around the communications. DNP3 however uses secure authentication features.

Modbus
Modbus is the most common protocol in use today for communications between programmable logic controllers (PLCs) due to its simplicity and free of charge. However, Modbus provides no security against unauthorized commands, data interception, or replay attacks. For this reason, Modbus over a serial communications link must be used with a bump-in-the-wire encryption and authentication device to add a secure wrapper around the protocol.

Simple Network Management Protocol
Simple Network Management Protocol (SNMP) is used for managing devices on IP networks. Through its history, SNMP has had several versions. Version 1 was discouraged due to poor security. Version 2 improved security but was later obsoleted. Version 3 addressed security and protects against data modification, eavesdropping (man-in-the-middle attacks), and masquerading.

IPsec
IPsec is short for Internet Protocol Security. IPsec encrypts and authenticates each and every packet of a communication session. IPsec is very strong at security and is used for creating secure tunnels (VPNs) between devices. I was once asked what my opinion was on SSH/SSL vs. IPsec. My answer? “IPsec has yet to be broken.

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