Chemical Engineering September 2018 - 46

2
3
1
Sensors on processing
equipment
Web server with process
control and monitoring
FIGURE 2. Shown here is an example of a replay attack, which can disrupt operations when messages
are intercepted for delayed transmission
communication (wired or wireless) is a
replay attack (Figure 2). For instance,
a hacker could capture an encrypted
message and retransmit it later to the
network. This delayed/repeated message
can cause potentially serious
negative effects throughout the entire
operation. For example, repeated
transmissions of a low-pressure signal
from a vessel could result in the
control system not shutting a valve
promptly to bring the process to a
safe state.
Best practices
Companies employing wireless sensor
networks, or any digital communication,
should use a network
security model (NSM) with multiple
layers of security, such as encryption,
device authentication and replay
prevention. Here are some best
practices to consider:
AES-128 data encryption. This type
of encryption, by the U.S. National
Institute of Standards and Technology
(NIST), supports a more reliable
and secure wireless network within
all communication systems because
it protects electronic data from intrusion
and ensures only designated
recipients can read the information.
When implemented on low-power
sensor devices, it protects against
data tampering. The AES-128 works
with a CBC-MAC algorithm on encrypted
payload data that generates
an authentication code sent along with
data. If any data are modified, the authentication
code becomes invalid as
they will not correspond to the payload
data. Therefore, the telemetry system
will ignore the sent data packet. Only
devices with the correct " key " will be
able to decrypt the data.
Device authentication. Device authentication
is a technique that ensures
that nodes within a network
pass an integrity check before joining
a network. An encrypted, onetime-use
token, along with address
information, passes from a node to
the joining network. The token is
decrypted by the gateway (or other
nodes already joined on the gateway)
using the network key. If the
node passes the integrity check
and decryption, it will respond with
a packet containing the token, address
information, and network time.
The use of the token stops a rogue
network from attempting to absorb
joining nodes and preventing them
from communicating with their intended
network. Additionally, this
process allows only authenticated
nodes to connect to the network.
Replay prevention. Replay prevention
stops a malicious device from
resending a message. A common
security attack is the capture and
re-transmission of a data packet. In
replay attacks, the encryption is not
broken but encrypted messages are
captured and re-transmitted. For example,
a message to turn on a relay
could be captured and resent at a
later time to disrupt operations. In
a way, a replay breach can be described
as a device analyzing a communication
to determine the start
and end of a transmission so it can
then copy and paste the message
ad hoc. Without replay prevention,
this message could be resent without
the receiving node knowing its
delivery was from an attacker.
For example, should an encrypted
message " to turn on a relay or
change the state of an output " be
captured and sent later, operations
could be at risk. Replay prevention
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Chemical Engineering September 2018

Table of Contents for the Digital Edition of Chemical Engineering September 2018