What additional benefits can QR codes bring to Bitcoin applications beyond payment requests?

Question

Anyone who has recently used one of the Bitcoin wallets on a mobile device (and some desktop clients) will have seen a Bitcoin QR code. Clearly, QR codes allow for a succinct method for transferring complex information in a reliable and error-resistant manner.

Naturally, the most obvious use of a QR code is for encoding a payment request URI. However, are there any other benefits that QR codes can bring to Bitcoin beyond this?

I'm thinking in terms of marketing, exotic transaction types that sort of thing.

Answer 1

In terms of marketing, here is a very nice QR code that could be used for spreading the word about Bitcoin. It contains a link to bitcoin.org. See this thread on bitcointalk.org for more information. It was created by phelix at bitcoinx.com.

Answer 2

You can use also use the standard bitcoin URI QR codes to transfer bitcoin addresses from one application to another. For instance you can show your Instawallet.com bitcoin address as a QR code and drag it into the MultiBit send bitcoin screen. (www.multibit.org). It automatically parses it and creates an 'address book' entry with the bitcoin address and label 'Instawallet'.

Similarly, you can generate a bitcoin QR code with a bitcoin address and your name as a label in the MultiBit receive bitcoin screen, copy it and print it on the back of your business card.

Answer 3

You can use QR codes with Shamir's Secret Sharing for making secure backups of deterministic wallets: http://code.google.com/p/bccapi/wiki/ManagingLongPassphrases

Answer 4

There was a thread on bitcointalk about creating a specification to encode additional data (besides the address) in QR codes. This would work with a key/value pair and it could be used for a lot of things. Here is an example for merchant/buyer interaction:

Merchant request for direct payment via bitcoin network.

Code:

btcpayment-request1: name=“My Bitcoin Inc.”; pubkey=1LGpwDU5djqsR1X14Tcass3y9fULTzxJq3; amount=300

Using this QR-code, the mobile phone knows enough to ask the user if they wish to pay 300 BTC to My Bitcoin, Inc. at the given bitcoin address. Presumably the mobile phone has the ability to make bitcoin payments, either directly (a lightweight bitcoin client) or indirectly via a payment API such as this.

Answer 5

If I recall correctly, a bitcoin transaction can be coded to require a password to access them. Therefore, you could make the QR codes a way to hold a bitcoin outside of a wallet.

Answer 6

I believe QR will be to BTC what paper is to cash. I even registered long ago QRBitCoins.com (and others) and am now waiting for the right project to prompt some work. I thought I should tell people in case there is any interesting on-going project that would need a good QR domain.

Answer 7

Inexpensive 2-factor authentication

A QR code could be used a contributor to a 2-factor authentication ("Something I have and something I know") system. When making payments a person could input a PIN as one part, and scan a QR code they carry with them in their physical wallet (could be printed on a plastic card for example) as the second part.

This approach could be used as a pre-authentication to provide the wallet application with temporary access to a private key held on the mobile device. This private key could then unlock the local wallet or act as an authentication key to a remove service.

It does have weaknesses though:

• A high-definition CCTV mounted near the point of sale could catch people whipping out their plastic card in preparation and a bit of image manipulation would harvest QR codes

• It's a bit fiddly and is probably only for the security conscious

Food for thought.