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By adding the element of a mobile device to verify the transaction it changes the dynamic here. There are protections and precautions to verify against fraudulent currency performed within the machine. The implied here is that there is no verification or protection (by means of storing values local rather then remote). In a system where there is transactional data / values stored, the default should be to have the data stored and housed within a protected system. IE central server that a simple app queries with API calls vs a database walled on a phone.

The same principles often come into play with online games and cheating, yet constantly developers make the same mistakes.