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It is very hard to clone a single modern SIM card or security chips in modern phones, the cost is significantly higher than 10K USD. So an off-line bank card or

It is very hard to clone a single modern SIM card or security chips in modern phones, the cost is significantly higher than 10K USD. So an off-line bank card or phone app holding, for example, up to 1K USD equivalent should be entirely possible. EDIT: I missed the problem with retailers. A shop needs to be able to accept off-line electronic payments and be able to hold it for days before syncing with a bank for such payments to be an alternative to cache in case of emergencies and then we are talking about sums that are worth for criminals to be able to access. So such system will need highly non-trivial security including physical security and may end up more expenses than simply using cache.

abdullahkhalids 2y ago
Let me explain a bit more what I am thinking. I imagine that the central bank issues many many 1 cent digital notes. Each note is unique (much like cash) with a unique private+public key. In this system, whoever holds the private key for a note owns the note (similar to cash). Now, the central bank also issues to each citizen a device that holds all the notes they own. If I want to give you a cent, I transfer the private key to you (by holding our devices close - no internet needed). But in order for you to trust that I indeed deleted the private key off my device, I need some sort of confirmation. This confirmation comes from a security enclave (consisting of a processor and the memory that stores the private keys) within my device. It should be able to emit a cryptographic certificate signed by some bank issued key that confirms the transaction. The idea is that security enclave can't be hacked to extract either the bank issued key or the algorithms that the enclave performs.
abdullahkhalids 2y ago
Re your edit: it's not just a question of crime. Once a shop excepts money, they should be able to use it. Even having to wait for sync for a few days can put people in the red. In my country, for example, it takes car-ride drivers to get their money from Uber/etc in about 1 week. So they almost entirely operate on cash. They need liquidity to pay for fuel and daily expenses.

abdullahkhalids 2y ago

Let me explain a bit more what I am thinking. I imagine that the central bank issues many many 1 cent digital notes. Each note is unique (much like cash) with a unique private+public key. In this system, whoever holds the private key for a note owns the note (similar to cash). Now, the central bank also issues to each citizen a device that holds all the notes they own. If I want to give you a cent, I transfer the private key to you (by holding our devices close - no internet needed). But in order for you to trust that I indeed deleted the private key off my device, I need some sort of confirmation. This confirmation comes from a security enclave (consisting of a processor and the memory that stores the private keys) within my device. It should be able to emit a cryptographic certificate signed by some bank issued key that confirms the transaction. The idea is that security enclave can't be hacked to extract either the bank issued key or the algorithms that the enclave performs.

abdullahkhalids 2y ago

Re your edit: it's not just a question of crime. Once a shop excepts money, they should be able to use it. Even having to wait for sync for a few days can put people in the red. In my country, for example, it takes car-ride drivers to get their money from Uber/etc in about 1 week. So they almost entirely operate on cash. They need liquidity to pay for fuel and daily expenses.