Topic: How to use bitcoin without a internet connection? (Read 3900 times)

So, we are nine months ahead in time. Using mobile internet abroad can still be expensive and sometimes even impossible. Being able to easily use bitcoin abroad is one of the key things that can make bitcoin adoption grow rapidly.

Do we already have a easy workaround for this issue, except for sms?

wow, I have received a lot of useful feedback. Thank you so much guys!!

Yep, definitely do-able.  Just need someone to bankroll the development of the system and market it to merchants.

I also thought about this; recently I was abroad at a place that accepts Bitcoin transactions, but wasn't able to actually pay with them (used cash instead) because my phone didn't have a 3G connection there (it would have been very expensive to allow it to use the foreign network).  It would be really great if it could become a kind of "standard" for point-of-sales and mobile wallets to allow me to create a signed transaction and have the point-of-sale scan it via QR code or NFC, validate it and broadcast it for me.

I believe that especially abroad it can help hugely to have Bitcoin acceptance because it decreases the need for currency conversions - but in those situations it is also hard to have internet access on your mobile phone to pay as long as there's no free WLAN around or so.  (Furthermore, if I use my 3G network to pay, the network operator and every agency hooked to its databases knows exactly that I was in the shop at the given time.  I may not want this in all situations, and also there it could be handy to pay with Bitcoins while the phone is offline.)

It would require that the vendor have a specially designed wallet for the purpose.  To make it safe for the buyer, there would need to be some new hardware for the buyer as well.

Think about the way that bitcoin works.  The buyer signs a transaction, and then broadcasts it only to the peers that the buyer's wallet is connected to.  Then those peers re-broadcast the transaction to their peers who re-broadcast it to their peers and so on.

So the vendor simply becomes the first peer.

The buyer would have a standardized piece of hardware that stores their private keys and that has enough logic in it to sign transactions.

The vendor would have a standardized piece of hardware that interfaces with the buyers hardware.

The buyer's hardware would provide (through the standardized interface) the vendor's hardware with a list of bitcoin addresses that the hardware can sign.  The vendor's hardware would then search the blockchain for unspent outputs and build an unsigned transaction that pays the vendors address with bitcoins under the buyer's control.

The vendor's hardware would then transmit the unsigned transaction to the buyer's hardware.

The buyer's hardware would display the transaction to the buyer so they could see that they weren't being scammed, and then allow the buyer to confirm that they wish to sign the transaction.

The buyer's hardware would sign the transaction and transmit it via the standardized interface to their first (only) peer, the vendor's hardware.

The vendor's hardware would then re-broadcast the transaction to all of their connected peers to ensure that the rest of the bitcoin network was aware of the transaction and that it would get confirmations from miners.

This is just one possible way to handle the transaction with future hardware.

It can be done today with the "Debug Window" on the Bitcoin-Qt wallet, but it requires some technical know-how and some way of getting the unsigned transaction to the buyer and the signed transaction back to the vendor.  It could be done by just typing it in, but that would be a big hassle and very inconvenient.  Bitcoin isn't ready for transactions like this yet, but it is technically possible.  We just need to wait for some enterprising entrepreneur to create and market the devices that will simplify the process.

how the vendor could brodcast the signed transaction? The vendor may only provide its address to the buyer. But the buyer has no internet, how does the vendor get a signed transaction? I thought in bitcoin system, it's the giver always initiate a transaction. Am I right? 

As long as the vendor has internet connection, then the vendor could broadcast the signed transaction.  There aren't any wallets that make this easy for the user right now, but it is technically possible (I just did it earlier today) and in the future I suspect there will be wallets that will make such activities easier.

It is only going backwards becuase you said that the fancy new "internet" technology is unavailable.  If internet was available there would be no need to use SMS.  SMS simply works as an old technology backup for situations where new technology doesn't exist.

A vendor should create a unique payment address for every tx so they *will* know exactly what payment to said address is for (and exactly where that "money" comes from should be of no concern).

I suppose what could happen is they have a load of empty paper wallets that the rider can pay with BTC from their smartphone. As long as taxis still accept cash, I don't see why this could be any less acceptable. Oh, but I forgot about confirmations...   

But the vendor may only verify the transaction, after the buyer has connected to internet and broadcasted the transaction. Am I right? that means the vendor still do not know if he or she has received the money or not, right on spot.

Because paying bitcoin is a one-way transaction. even the vendor has internet on spot, he or she has no clue about where the money is coming from.

If vendor cannot confirm a transaction on spot, then bitcoin is a lot worse than dollars.

It doesn't look like very convenient to me. Bitcoin have to port to old phone SMS system? It is going backwards.

 

Perhaps in the future, there will be trusted, insured, audited online wallets.

Then you could store your bitcoins at the online wallet and send a txt message to transfer the bitcoins to the taxi's online wallet.  Then the taxi's online wallet could send them a confirmation txt message letting them know that they had just received the bitcoins.  The online wallet could even offer a dial in automated voice system for sending and confirmation in case SMS was down.

It would be possible to construct a "raw transaction" and then find some other way to broadcast that, however, it would not be very convenient method and of course the seller would still need internet connectivity in order to verify that the tx gets confirmed.

You can sign a transaction offline, but the vendor will need access to an internet connection at some point in order to get the transaction recorded in the blockchain.

hey, I read from some place it says people may use bitcoin to trade when there is no internet connection.

For example, you are using smartphone bitcoin wallet, and now you are paying your taxi fare. but you phone's internet is down. you still can pay the bill by using bitcoin from your wallet.

As far as I can understand, I think this is because your blockchain in your wallet is up to date. so, the transaction will be confirmed when you have internet. however, I am not sure how the taxi driver(the receiver) is going to stop worrying if you will not reconnect to internet?  how does the taxi driver know the payment is finished right on spot?

I really have some trouble to figure this out, please help me. this is really important. Internet is not always reliable, but people always need to buy stuff!!

 thank you so much for your help!!!