New revolutionary double locking system, mechanical and electronic. This is a cylinder equipped with one set of standard keys plus a special key, “C-KEY”, that once inserted, is able to program the operation or the non-operation of any of the other ones. In case of loss or misappropriation of one of the keys, through the “C-KEY”, that missing key can be deleted from the list of the authorized keys, and so it will not able to open the lock anymore. It is also a very useful solution for those who need to change their locks often, depending on the real user of the door (guest, tenant, staff, etc…) On request, OKEY can set this locking system in all the models of doors that carry cylinder locks, or else supply the convenient case containing the special cylinder, the set of standard keys and the coding key “C-KEY”. A technologically advanced system, but also practical and easy, that will make the use of your lock safer and up-to-date, without need of replacing it!