Clearing out RFID key memory?

Hi everyone! New member here with a new (used) 2003 Prius. I got the car with just one master key, and I've already bought and associated a second one using one of the "chicken dances". I've been trying to learn as much about these dances as I can, and I've found that for keyless entry fobs the dance that adds a fob has a variant that also clears out all existing fobs other than the one being added. Anybody know if there's a variant of the key add dance to clear out associated keys? Would be nice to know that any other keys past owners had for the vehicle no longer start the car.

And if there's no dance for it, has anybody done anything like this using onboard diagnostics or other more advanced methods? I found someone's dump online of the ECU EEPROM that apparently stores these key IDs, but messing with that is a risky proposition.

 

Well a couple years later and I have the Toyota repair manual for this vehicle, and these procedures are all in there. They're in the Body Electrical section of volume 2.

For the remote unlock fobs, the subsection is called Wireless Door Lock Control System and the instructions are in step 2 under Replacement. The rewrite and prohibition modes both erase all existing codes.

For ignition keys the subsection is Hybrid Vehicle Immobiliser System. The procedure in step 9 erases all master and sub key codes except the master key that's being used for the operation, in a similar fashion to the rewrite mode for the wireless lock system.