Many thanks for this additional information. I had no idea that the master key was not used on the blockchain. That would mean the created public keys would need to somehow be reproducible so that when a master key is used, the chain can 'know' it was the one that produced the public keys. This whole key-creation idea is amazing and mysterious to me. I'm amazed that a machine can decode any of the keys given to it and 'understand' that those keys came from a particular master key.