The wiki instruct that you should use Rebug Toolbox to dump the eid_root_key. Unfortunately I couldn't get this method working on CFW 4.90. When I select the "Dump eid root key" option, nothing happens. I don't know if its me or my console.
But if you are running evilnet 4.88.2 or higher, this is available on the PS3 XMB itself as explained here (https://consolemods.org/wiki/PS3:Recove … _Firmwares).
I thought it would be nice to have it added on the Wiki, and to ask someone else to check if it work for them.