backing ecash

Now obviously, things would work a lot more smoothly if you didn't need me or my digital currency exchange. It would be nice if Bob and Alice could buy and sell edollars from their banks online. But it's not essential. I

Isn't there a problem with net-based distribution of ecash? It would seem that Eve could intercept the ecash and spend it first. Encrypted email return of the ecash would seem to violate the anonymity of the ecash. Some sort of one-time encrypted return address would seem to be necessary, but better yet would be a vending machine that took a floppy disk and some currency and stuck the ecash on the floppy. Paul