>Bob exchanges currency B for currency A with Alice. Alice now holds some currency B
There is no reason for Alice to want B, a less secure money than A which they already hold. If Alice were perfect mathematician, this exchange would never occur.
There is no reason for Alice to want B, a less secure money than A which they already hold. If Alice were perfect mathematician, this exchange would never occur.
Oh, and then there were cryptocurrencies C, D and F too, but that's a different thought experiment.
If a transaction does not do this, it can be guaranteed to be insecure.
>Faster block times means she'll get her coffee sooner
Maybe. Or maybe the merchant doesn't get paid for coffee at all (because faster blocktime means more orphans)!