Jack Buyer and Alice Seller agreed to use bitcoin on their large deal.  It was rumored to be in the 10-100 kBTC range.  This was well more than an average years salary range in the tropical location they now resided.   

Alice wasn't going make Jack pay upfront before seeing the goods, but to keep things simple they agreed on the price beforehand. 

When Jack arrived Alice had the wares out and safely displayed in a requested location, a location with litttle to no external communications available.   

Jack took a look at the goods, raised his eyebrows, and agreed to pay the price. 

How did the deal go down?
Is there anything Jack and Alice could do to make their deal go down smoothly and with minimal button-pressing or waiting?     


 


Here is one scenario:

Before the deal Jack moves some funds around publicly between wallets to prove he has the cash handy and so she knows the public address of the coins in question.

At the location, Jack hands over the private key to those coins, a QR code he has kept in his wallet or perhaps a base 56 string from memory. 

Alice verifies on the spot that Jack's key matches the public address they agreed to, using an ECDSA sig checker widget on her phone, after cursing at her OCR/VR software a bit.   

At this point Alice trusts Jack, and offers the goods and tells him he is free to go..  however Jack is more suspicious.  He fears Alice's organization and doesn't want to leave them with room to accuse him of anything should the funds move before Alice expects them to. 

So he waits while Alice phones an accomplice, and uploads to her the key.  The accomplice moves the coins to a new address and they wait six blocks while drinking six beers.