No, it's not done on-device. Think about it: they know where the merchant is for...

ThePowerOfFuet on Feb 22, 2022 | parent | context | favorite | on: Apple unveils contactless payments via Tap to Pay ...

No, it's not done on-device. Think about it: they know where the merchant is for card-present transactions, so how do they know how far apart the card and your phone are if they don't know where your phone is?