Auto Generate Machine Key VS. Custom Machine Key

Question

We have load balancing on servers, and as you know we get the Mac Failed Error, after some search we found that Use Custom Machine key in all servers instead of auto generate config,

So the question is what is the difference at all?

Is there any security risk when we use Custom (fix) machine key?

Answer 1

If you have a WebFarm you have to use custom machine key, other way it won't work.

The only secure problem is that there are people, who knows these machine key. If they "sell it" outside your company somebody can for example decrypt your cookies.