Can the blockchain be used as a 2 factor authentication?

[snakus44]

Very simply put, say I want to sell a digital file, a song mp3 download, or even just a single song play.  It'd be nice if there were a program out there which allows users to listen to practically free music, without ripping artists like Spotify and the other big boys.  So I was thinking, what if this new music listening program verifies that the user has paid for the song(lets say $0.025), by taking a random portion of the block chain + info from the most recent block + songinfo + user info to authenticate the purchase and allow the program to play the song.  I guess its not exactly 2fa, but it would be a way that could authenticate ownership of digital material that would change every 10mins.  Am I even close here?   

[zorke]

One thing that would be very similar to this would be to set up a payment address that users can send bitcoin to buy the song. Users must use only one sending address to make this payment. Then you can have the user sign a message from an address that had send the address you setup at least $.25 worth of bitcoin in the past

[shorena]

Sure its possible but IMHO loading DRM data into the blockchain is not a good idea. I am biased though because I think DRM is not a good idea and I thought the musicindustrie was finally over with it. Just sell MP3s, no DRM and make payments easier and better than pirating. Bitcoin seems very good for that .

[DannyHamilton]

One thing that would be very similar to this would be to set up a payment address that users can send bitcoin to buy the song. Users must use only one sending address to make this payment. Then you can have the user sign a message from an address that had send the address you setup at least $.25 worth of bitcoin in the past

There is no such thing as a "sending address" in bitcoin.

It's true that some services have attempted to look at the scripts that were associated with the unspent outputs when the outputs were created to find an address that they could call a "sending address". It's also true that in a subset of cases this attempt seemed to accomplish what the service wanted to do.  However, it's improper use of the information available to make educated guesses with an unreliable result.

Services that do this should be avoided.  If someone is asking for a "sending address", then they don't understand how to use bitcoin safely and cleanly, and they are therefore likely making other more significant mistakes in their systems and processes.  The safest thing to do would be to take your business elsewhere.

[franky1]

the blockchain can be used as 2FA.. checkout bitID http://bitid.bitcoin.blue/

the simple method is that your service registers a customers public key (never request private key). and then to log in it asks your customer to sign a message using that address. (bitcoin sign message feature of most bitcoin client programs)

now as a separate subject of the music idea.
imagine you opening a itunes rival or a website to rival microsoft office download store. where they use 'product licence keys'. well the simple solution is that your service creates public and private keypairs and for each customer download. you give a customer a bitcoin public key(dont give customers your private key). and then to allow the download of the actual program/song, the customer has to make payment.