ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 97)

m is the input message of arbitrary length converted to a bit stream.

pad

consists of pad bits (1 followed by 0’s) concatenated to m such that the length of m

ext

congruent to 448, modulo 512.

is the length, in bits, of the original message, m, expressed as 64-bit binary blocks.

The extended message, m

ext

, is subjected to four rounds of bit transformations where

each transformation includes 16 operations. On each operation, a fixed value is added to

the result. This fixed value added to each result of the 64 operations (different value for

each operation) is calculated using a SINE function and stored in a 64-row table (one row

for each operation).

A fixed value calculated in the following way is therefore stored on each row:

Addition = int(2

× abs(sin(i)))

where i is expressed in radians.

These 64 fixed numbers (addition) will never exceed 32 bits.

Security in HomePlug AV

The main security functionalities implemented in HomePlug AV are the following:

•

Encryption based on 128-bit AES in CPC (cipher block chaining) mode;

•

Data protection using a NEK (rotation of NEK values every hour) encrypting

the physical data;

•

Authentication to join a PLC network using a NMK (network membership

key) used to distribute NEK over the network;

•

New PLC device authorization by configuration:

•

using a frame carrying the NMK over the Ethernet interface;

•

using a DAK (direct access key) key corresponding to the DEK key of

HomePlug 1.0

;

•

using the easy connect button;

•

using a MDAK (Meta DAK);

•

using a pair of PPK (public-private key encryption);

•

Support of HLE (higher layer entities) protocols, such as IEEE 802.1x.

Table 4.1 summarizes the security management characteristics of the various

PLC technologies with their key management, encryption level, advantages, and dis-

advantages of each method.

Attacks

As we have seen at the beginning of the chapter, the purpose of an attack is not

restricted to the connection to a network in order to recover data via flaws in it. An

attack can also be intended to disturb network operation, both at the network and

physical levels.

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 97

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