Slapping stickers on something is not a scaling issue. The secure storage and transmission of private keys is. The idea that you&#x27;d just slap the private key on a sticker and have no other record of it is not something I even considered because that&#x27;s very user-hostile behavior (unless they already have the intention to mod the device software before they buy it, they&#x27;re unlikely to retain the sticker). It also screws with the secondhand market, both because secondhand devices won&#x27;t have their key, and because the original owner obviously had access to the key and could have tampered with the software on the device before selling it.