The cmd option is used to specify an SDF command whose SYSOUT outputs are to be used as an entropy source. You can specify this option as often as you wish. The commands specified here are entered in a list which is processed cyclically at intervals defined by the cmdInterval option.
Multiple specification of the same command is possible. This can, for example, make sense for commands whose SYSOUT output changes considerably more or more frequently than that of the other commands specified.
cmd |
<sdf-command-name> <entropy-rate> |
<sdf-command-name>
Name of the SDF command whose SYSOUT outputs are to be used as the entropy source.
<entropy-rate>
Estimated relative entropy content of the SYSOUT output of the command specified under <sdf-command-name>.
Example
In this example it is assumed that a line of a SYSOUT output of the SDF command SHOW-USER-STATUS INFORMATION=*PROGRAM is 40 bytes long and that there are 16 different, equally probable variants of each of these output lines. The latter means that a task executes one of 16 given programs with equal probability.
In this case each of these lines contains half a byte of entropy and the entropy rate is correspondingly 0.5/40 = 0.0125. In practice it is much more difficult to determine how many different outputs can occur. Furthermore, these outputs are rarely equally probable. However, specific, plausible assumptions regarding the number and probability of various variants of an output line (see above) can be made to estimate the entropy rate and, as required, to reduce this by a safety factor.