

Or, if the app has the private key for decryption for the user to be able to see the messages, what’s stopping the app from copying that decrypted text somewhere else?
The thread model isn’t usually key management, it’s more about the insecure treatment of the decrypted message after decryption.




Visa/Mastercard requires all cardholders, cardholders’ banks, merchants, and merchants’ processors to follow the comprehensive set of rules for disputed transactions. That way the dispute process tends to be uniform across different banks and across different merchant/payment processors.
The network sets the rules, while the banks implement those rules on behalf of the cardholder and the processor implements those rules on behalf of the merchant.
So replacing the network will require a comprehensive replacement for the network’s dispute resolution rules (assigning who is responsible for paying when certain things happens) and procedures (how a cardholder can initiate a dispute and how that gets resolved).