In step 3, who decides which to 'unblind' and do they have visible uniqueness identifiers to ensure that Gregory actually opens those ones?
And since it's not stated explicitly, I assume by "checking everything's ok" the bank verifies that each has a unique ID they haven't already got, money values are all the same, and the id pairs all work out to a valid address.
On second thought, Gregory and the merchant just have to collude to fake the identity string half. Even if uniqueness matches, the bank won't know who to punish if it's incorrect.
And since it's not stated explicitly, I assume by "checking everything's ok" the bank verifies that each has a unique ID they haven't already got, money values are all the same, and the id pairs all work out to a valid address.
On second thought, Gregory and the merchant just have to collude to fake the identity string half. Even if uniqueness matches, the bank won't know who to punish if it's incorrect.