> By their very nature efuses can be programmed only once. You can never overwrite the old values with arbitrary new values. My understanding is this: you cann

> By their very nature efuses can be programmed only once. You can never overwrite the old values with arbitrary new values. My understanding is this: you cannot overwrite the old values, but you can blow an additional fuse. If you have five fuses, then you blow the first fuse for the first key, then the second fuse for the second key. When you blow the second fuse, the system will only look at the second fuse, then the third, etc.