Also if slaved, to access the device directly w/o going through the master node adds two more to the number of success required. Of course there is still that problem of mutual signal range. Mouse wouldn't want to be close enough to have to directly hack a cyberarm or skill wire set.
Theoretical question: cyberware even at signal 0 have what...about a 3ft range? Which is in mutal signal range of your com-link. That would form a mesh network and therefore would be hack-able, would it not? Even if the devices are hidden. So either slave it or not slave it, doesn't seem to make much difference, you can be hacked either way. It seems the best option for not having your cyberware hacked is to not have cyberware at all.
From the encryption standpoint: it seems to me that each device would need to run an encryption program to encrypt the data that is being transmitted back and forth. Encrypting a node would entail encrypting all the data stored in the node (which is why bio-nodes can't be encrypted since they can't store data there, but could still run an encryption program for handling team/internal data traffic) and would need the encryption program running??? for the node to decrypt it??? in order to access its own data.
At signal 0 that's 3 meters, and this is within Tony's commlink. It was to easy to even ask you for a roll to hack, this, I guess you hacked his link as a matter of bad habit. The devices are hidden, btu Omar has found them.
slaving give you a +2 for the difficulty to hack them directly.
the other best option is to load it with IC, like every sane citizen is doing, but somehow runners never do.
also encrypting a node doesn't entail encrypting the files (pg 66, Unwired)
the other best option is to do what the Amy is doing, but I'll leave you at guessing how
you can run decrypt/encrypt complex forms in your bionode, you just cannot encrypt node.
sorry for the mixed aneswers