Compaq WL110 User Manual page 100

Notice that in the transition periods 1, 3 and 5 the end users can switch over from
one Txkey index to the next. At the end of this period, all stations must be over
to the new key index. Transition period 7 includes the transition to a new set of
keys as well. The total length of time a key is used consists here of the main life
time period and two transition periods. Assuming the main life is much bigger
than the transition, this can still be considered to be a single key scheme,
because most of the time only a single key is in use.
Alternative Schemes
Alternative schemes can be envisaged, which have main life periods in which
two or more keys are active. An example is given in Table7-3
Table 7-3 Alternative Schemes
Period
# Description
0 Main life key A A-0-0-0
1 Main life A+B
2 Main life B+C
3 Main life C+D
4 Main life D+E
5 Main life E+F
Table 7-3 gives a scheme where at each period two keys are in use; at the end of
each period, the oldest key is no longer valid and needs to be replaced at all
stations. Advantage of this scheme versus the scheme in Table 7-2 is that it
requires less frequent configuration changes at all Access Points.
Security
7-18
AP Configuration
Keys 1-2-3-4 Tx Key
1
A-B-0-0 2
0-B-C-0 3
0-0-C-D 4
E-0-0-D 1
E-F-0-0 2
Out- STA
ward Configuration(s)
Keys 1-2-3-
4
A A-B-C-D
B =
C =
D =
E A-B-C-D
E-F-G-H
F E-F-G-H
In-ward
Tx Key
1 A
1|2 A | B
2|3 B | C
3|4 C | D
4 D
1 E
1|2 E | F