Subject: Re: [Bitcoin-development] Paper Currency

From: Andreas Schildbach <[email-masked]>
Date: Sun, 18 May 2014 14:14:51 +0200

> One problem we couldn't figure out here though - how to protect the
> notes from unauthorized redeem. Like if someone else tries to reach your
> wallet with his own NFC - how can we distinguish between deliberate
> redeem by owner and fraudulent redeem by anybody else with custom built
> long range NFC antenna? Any ideas?

I think you'd need multiple factors to protect against that attack. Like
encrypting with a key that is printed on the note as an QR code.