Bitcoin Forum

So. I've been using bitcoin for far to long to not know this... But here it is...  ???

Lets say hypothetically i want to send someone some Bitcoin, and that person gives me their address. But they get's a lot of bitcoin from many people all the time on that same address.

How do i tell them what my sending address was?

I google'd and nothing useful came up... I looked at my previous transactions with blockchain.info and they seemed to have different sending addresses.

Is this even posible?

PS. I'm using the standard Bitcoin-Qt wallet


Hello other forum newbies...
Please use this thread to spam your posts after my answer has been answered. Thanks.  :)

You could instead give them the transaction number. I think that would be more useful, since it would show the total amount sent, even if it's from many addresses.

If you use Bitcoin-QT you can send money to him.
Then copy the transaction id and post it at blockchain.info
You will then see your sending address.

Btw, is there any other Bitcoin Wallet out there that lets me specify my own sending address?

The receiver *should* be giving you a unique bitcoin address for you to send the coins to if he wants to be able to tell when he received them.  It is a "best practice" to use a new bitcoin address for every transaction, but they should at least be using a separate address for each sender.

Assuming that the receiver has failed to do this, the next best thing would be for you to provide them with a transactionID.

The problem with you providing some sort of information (such as a transactionID or a "sending address") after the transaction has been sent, is that you could just search the blockchain for a transaction that someone else sent them at that address and "claim" that it was you transaction and you address.  How would they know if you were telling the truth or not?

I'm not sure, but I think Armory might have that level of control.  There is a "coin control" version of Bitcoin-Qt that someone created. I've seen links to it before here at bitcointalk.org.  I'm not sure how trustworthy it is, but if you search a bit for "coin control" you can probably find it.  I think it was called "Yet Another Coin Control" or something like that.

https://blockchain.info/wallet allows you to choose which addresses you "send from" with the "Custom" transaction type.

Yes i always make a new address for every transaction. Thats what confused me too.. I will just use the transaction ID.

Thanks.

you should always send only from an address you can sign a message with. That´s very useful for matters like this, if you sign the message you can prove that the payment address is yours. Follow this steps when you have to sign an address http://imgur.com/a/nUmZ0, send the other person your address and ask for a message to sign, after that the other part just have to verify it.

And how would you suggest choosing the address that you send from?  Most of the wallets out there don't have such an option.

what are you talking about, it's easy as 1, 2, 3, of course you need a wallet with that capability but is not that hard find one, bitcoin-qt has it.

???

Err... either you've misunderstood or you know of something new that most of us isn't aware of. Can you show us how to do it or provide an explanation on how to go about the procedure?

is the alphanumeric code .....

Lets answer the original question.

"Lets say hypothetically i want to send someone some Bitcoin, and that person gives me their address. But they get's a lot of bitcoin from many people all the time on that same address.

How do i tell them what my sending address was?"

Why verify messages? In case another person claims that your payment is his payment you have to be able to prove that the address you sent from is yours.
You need a wallet client that can sign messages like bitcoin-qt and follow these steps, in your client go to file and then to sign message after that you will see a screen like this https://i.imgur.com/aZjRyKX.png there you sign your address with the message you want (something arranged between the two parties) and click sign message, in the signature zone will appear a unique code.
After that you can send the information to the other person and ask them to verify it.
That way you can prove the address is yours.

So, simply as that you should control your transactions carefully and when someone ask for "what's your address I have a lot of payments to that address and I'm not sure that one is yours" you can send them the information they need to verify it.

Yes, you can sign a message with an address. But you can't choose which address the wallet uses when it sends the bitcoins.  There is no way to know that the wallet will use bitcoins that were previously sent to that address.  As a matter of fact, the wallet could use bitcoins that were last sent to a "change" address.  If it does this, then the address does not show up in your "Receive Coins" tab.

It is not safe to rely on concept of "sending address" in bitcoin in general. Look at this thread (https://bitcointalk.org/index.php?topic=196953.0).

you can find the address in the blockchain with the Transaction ID, that's why you SHOULD use a wallet you can control.

Sure, but you said:


My point was that Bitcoin-Qt is NOT a wallet where you can control which addresses received the coins that you are sending.

I was talking about this.



I think you lost the track there. Of course you can control which address will receive the BTC, what you can't see is which address sent the transaction when you receive some coins but you can find it with the blockchain.

Nah, I didn't lose the track, I suppose I just didn't find a good way to explain what I was trying to say.

When sending bitcoins, you can't choose which addresses previously received the particular bitcoins that your wallet sends.  Your wallet chooses that for you.  You can choose what address you send them to, but you can't choose from all the addresses that previously received bitcoins, which addresses should be used as the "sending address".

Now, you say that you can "find it with the blockchain", and this is true.  After you've sent the bitcoins you can look at one of the blockchain parsing websites and find out which addresses previously received those bitcoins.  However, if the address was a change address, then you have no way of signing anything with the private key of the address as far as I know.

Actually, if you add one of your own change addresses to your address book, it will get added to your list of receiving addresses, and then you can sign a message with it. This fact is known to almost nobody, as almost nobody ever has to actually deal with change addresses (and ordinary users never do).

Nobody ever has to know what their sending address is either, especially as if you use an e-wallet, your sending address will not even belong to you. If anyone ever asks you about your sending address, they're doing something horribly wrong.

Interesting.  You learn something new every day.  I'll have to try this. Thanks.

Thanks