
Decryption Attacks
The purpose of this attack is to try to discover the NEK of a PLC network in order to
connect to it and to recover the exchanged data.
The two following techniques are used to discover the NEK in HomePlug 1.0:
•
Have access to the physical frames and store enough frames so that they can
be decrypted using suitable algorithms. However, this technique is very com-
plex and requires expensive specific hardware solutions.
•
Try out all possible combinations of NEK to have access to the network.
The time that is necessary to try out all the possible combinations of NEKs can
be estimated in the following way: the NEK is encoded with the DES-56-bit algo-
rithm derived from a password entered by the user of the PLC network, which may
vary from 4 to 24 characters.
Therefore, the maximum number of possible attempts is:
N =≈ ×2 2 88 10
58 17
.
For a 64-byte Ethernet frame with a 100-Mbit/s network interface card, the
transmission time is:
T
frame
=
×
××
≈×
−
64 8
100 1024 1024
488 10
6
bits
,,
.sec
The total time which is necessary to try out all combinations then is:
TNT
total frame
=× = × × × ≈ × ≈
−
288 10 488 10 14 10 44
17 6 12
. . . sec ,591 years
Security for PLC Networks 79
Table 4.1 Encryption-Key Management According to PLC Technology
TECHNOLOGY
KEY
MANAGEMENT
ENCRYPTION ADVANTAGES
DISADVANTAGES
AND FLAWS
HomePlug 1.0 NEK DES-56 bits Simplicity
– DES shortcomings
– A single key for
each device
HomePlug Turbo DEK Same Same Same
HomePlug AV
– NEK
– NMK
– DAK
AES-128 bits (key
rotation)
High encryption
level
Possible shortcom-
ings with easy con-
nect button
Ascom Key exchange
RC4 + Diffie-Hellm
an (128 bits)
Configuration made
easier by interface
RC4 shortcomings
DS2
Master-slave key
exchange
3DES
Central configura-
tion by administra-
tion console on
master device
Interception of key
exchanges during
authentications
Oxance
– NEK
– DEK
– DES-56 bits
– AES-128 bits
Management by
Web centralized
interface
Possible Web inter-
face shortcomings
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