fair enough.
first of all, you can protect the file.
If you don't protect the file than anyone can read the file.
the protection is a edit file action with a simple Computer + Logic [Data Processing] test.
to get a good protection you need to protect the file on a decent device (but you can also use a limit breaker on the roll). Protecting a file is a Data Processing action, which means everyone - even non-hackers - can do it. And you can protect files even on a normal commlink.
This will prevent people from reading it.
The only way unauthorized people can read the file is if they first break the protection and this is done with a matrix attack action. As the owner you will be informed if/when someone kill your file protection. Crack File is resolved with Hacking + Logic [Attack] v. Protection Rating x 2; so on this roll you don't really get any help if the file is stored on a high rating device.
Crack File also require a mark on your cyberdeck/commlink. Either with Brute Force which is resolved with Cybercombat + Logic [Attack] v. Willpower + Firewall or Hack on the Fly which is resolved with Hacking + Logic [Sleaze] v. Intuition + Firewall. In both cases a higher rating device will make it harder to achieve the initial mark, but you could have a low rating device slaved to a high rating device to take benefit of the high rating device's Firewall.
To set a data bomb you resolve it with Software + Logic [Sleze] v. (Device Rating x 2)
This mean you can not use a commlink to set a data bomb on a file, but you can use your cyberdeck to put a data bomb on files that are located on your commlink. You require at least one mark to set a data bomb, but if it is your commlink we are talking about this is not an issue at all. The data bomb have the potential to be stronger on weaker devices, so in this case you would want a low ranking commlink (preferable currently not slaved to a master device with a high firewall rating).
To remove a data bomb is resolve with Software + Intuition [Firewall] v. Data Bomb Rating x 2. There is no need to have a mark in order to remove the data bomb and the limit is Firewall: This all mean your opponent can remove it with a (high rating) commlink.
To sum up.
Buy a low rating commlink (use it as a team file server) and slave it to your cyberdeck or a high rating commlink (just for the extra firewall dice). Store your files on the low rating commlink. Use Edge to break the limit when you place a protection on the file located on the low rating commlink. Log in to your cyberdeck and set a data bomb on the file. Slave your commlink to your cyberdeck or a high rating commlink.
You get to use your intuition or willpower to protect against hackers trying to get marks. You get to use a high rating firewall dice as well. The data bomb will be deadly++ since you did it on such a low rating device (odds are you will brick the cyberdeck or commlink being used to disarm the bomb if they fail - causing dump shock if the operator disarming the bomb from VR). The protection have potential to be very hard and time consuming to break, automatically dealing unresisted matrix damage on each failed attempt.
