The recipient needs internet access. I plan to use this method if I for local, in person sale of my bitcoins for cash.
For example: I have a localbitcoin ad to sell 10BTC. Someone responds and we meet wherever he is comfortable with his internet access. I print and fund a 10BTC bill before going out to meet him/her. We exchange cash for paper, and they transfer the coin to there own wallet. Yes, they should have access, but I don't need anything other than my printed coin. I don't have a smart phone so this is ideal for me.
[...]
- So only the recipient has internet access in your example: he doesnt want to hand you cash until he sees the private key you are handing over actually has money in it. So he can scan it, hand it back and say it was already empty and runs away. Well he just stole the coins.
- (Well just let him scan the public key and not the private one) well ok in that case you can scam him by NOT putting the REAL private key under your thumb
- He doesnt want to hand you cash until he knows he can get bitcoins, you dont want him to scan any private key until you have cash
Have you never bought or sold anything in person? If you put the coin there, you know it's there. The other party saying it isn't and running off is no different than just plain stealing it in the first place. Actually, you even have proof that you funded the address.
If that requires escrow, everything requires escrow.