> Also, how is "there will never be another certificate for the same thing, from the same brand of certificates" technically enforced? A Merkle chain[0] append

> Also, how is "there will never be another certificate for the same thing, from the same brand of certificates" technically enforced? A Merkle chain[0] append-only ledger contains a transaction minting the certificate, and the consistency rules for that Merkle chain mean that any extension of the chain which mints another such certificate is not valid (the same as a extension that spends money from a account with no money in it is not valid). 0: technically a blockchain specifically, but that's not actually relevant