Rohan Hill • over 11 years ago
Conceptual question - Preventing Double-Spending Offline
"MintChip works online and offline (...) and enables easy person-to-person payments."
I'm having trouble understanding how MintChip solves the double-spending vulnerability when used for offline person-to-person payments.
- Dennis the Menace
Suppose Dennis has a rogue MintChip implementation that has been modified to "conveniently skip" the step of decreasing his own balance after sending a payment. The following transactions occur offline, so there is no access to a centralized resource (server) during this scenario.
Emily, in good faith, receives a successful transfer of MintChip currency from Dennis. Dennis does not decrease his MintChip's balance, instead, he meets Sarah, and transfers to her the same funds that were previously sent to Emily.
If neither transaction was done "online", then how does Sarah's MintChip implementation know that Emily has already been transferred the same MintChip balance that she just herself received a duplicate of? There is no opportunity for communication with a central/common record.
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