Single-use stickers, sent as a roll to the supplier at their registered address. Like a one-time pad of proofs. Each sticker would just be a QR code containing an HMACed {shipper ID, sequence #} string.
When Amazon receives the stock, it adds the sequence # to the set of sequence #s used/acknowledged for that shipper. If there’s a collision, the shipper gets a strike against it (because it’s their responsibility to protect their sticker roll from copying) and the item itself is returned-to-sender as undeliverable (because it was very likely a counterfeit.)
When Amazon receives the stock, it adds the sequence # to the set of sequence #s used/acknowledged for that shipper. If there’s a collision, the shipper gets a strike against it (because it’s their responsibility to protect their sticker roll from copying) and the item itself is returned-to-sender as undeliverable (because it was very likely a counterfeit.)