ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 92)

Therefore, a PLC logical network is based on an encryption key called a NEK

(network encryption key) in the HomePlug specification that encrypts the data

exchanged between the various PLC devices (see Figure 4.10).

A PLC network can be configured with a NEK in several ways:

•

Via the Ethernet interface. A configuration frame of the NEK is sent in broad-

cast mode to the PLC devices of the same network using a configuration tool.

All the PLC devices connected by means of their Ethernet interface recover

this configuration.

•

Via the electrical interface. A configuration frame of the NEK is sent by means

of the electrical network to the connected PLC devices. This is only possible if

a second key, called DEK (default encryption key) is known. This key, which

is specific to each PLC device, is recorded in the device memory by the manu-

facturer by following HomePlug specifications. The DEK is used by two PLC

devices—the configuring station device and the device which must receive the

new NEK—for the encrypted NEK exchange over the electrical network.

•

Via a Web interface. If the PLC devices are advanced, like those of the Asoka

USA brand, the key configurations can be managed by a single Web interface.

Access to the Physical Medium

In Wi-Fi, the transmission medium is shared. Therefore, anyone in the network cov-

erage area can intercept its traffic or even reconfigure the network at will. In addi-

tion, if a malevolent person is rather well equipped, this person does not need to be

in the network coverage area. The person just has to use an antenna with or without

amplifier assistance to have access to it.

In the case of PLC, the transmission medium is also shared, but the access to the

physical medium is much more difficult and especially potentially dangerous.

Security for PLC Networks 73

Figure 4.10 PLC logical networks with various NEK

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 92