How can a person prove that a Bitcoin transaction has been sent by them?

[BeatsBearsBattlestar]

Hi guys, I want to crowdfund a project by means of Bitcoin donations. The setup is very simple: I have a Bitcoin wallet, and everyone who sends any money to it gets a little something in return.

The only problem is that I have no way of confirming which person is behind every transaction. Is there an easy and surefire way for the senders to sort of "sign" their transactions, to be able to prove that it's theirs?

[buwaytress]

You answered your own question actually... yes ask all senders to sign their sends.

However, if you're only sending back to senders, then it shouldn't matter as you only need to cross reference all spends to you and send back returns to the corresponding addresses.

[MadGamer]

Assuming that you have a website or a mobile app to do that, It shouldn't be hard to do. All you got to do is generate a new address for each user and ask them to send a specific amount to that unique address , after the transaction receives at least 1 confirmation you credit him with whatever you was planning to give him. It's better to use a payment processor like Bitpay to make things easier for you.

[shorena]

Not everyone will be able to sign a message[1]. I suggest you create a deposit address for everyone that wants to participate.

[1] https://bitcointalk.org/index.php?topic=990345.0

[BeatsBearsBattlestar]

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.

However, if you're only sending back to senders, then it shouldn't matter as you only need to cross reference all spends to you and send back returns to the corresponding addresses.

I'm not going to send them money back, or any other digital asset. They are getting a service in real life, so I have to know who's who.

[OgNasty]

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.

It depends on what client you're using.  Basically, the sender just uses the address the coins were sent from to sign a statement proving to you who they are.  Then you use your client to verify that the message goes with the address.

Using core, here's what the sign message screen looks like:

[shorena]

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.
-snip-

I guess the subtle hint was not enough.

CLICK HERE TO LEARN HOW TO SIGN A MESSAGE WITH VARIOUS WALLETS, HOW TO PRESENT THE MESSAGE TO OTHERS AND WHICH WALLETS DO NOT ALLOW YOU TO SIGN -> https://bitcointalk.org/index.php?topic=990345.0

[BeatsBearsBattlestar]

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.
-snip-

I guess the subtle hint was not enough.

CLICK HERE TO LEARN HOW TO SIGN A MESSAGE WITH VARIOUS WALLETS, HOW TO PRESENT THE MESSAGE TO OTHERS AND WHICH WALLETS DO NOT ALLOW YOU TO SIGN -> https://bitcointalk.org/index.php?topic=990345.0

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.

It depends on what client you're using.  Basically, the sender just uses the address the coins were sent from to sign a statement proving to you who they are.  Then you use your client to verify that the message goes with the address.

Using core, here's what the sign message screen looks like:

http://i41.tinypic.com/6tg313.jpg

Right. Thank you very much for your help guys!

[Aamir1]

Hi guys, I want to crowdfund a project by means of Bitcoin donations. The setup is very simple: I have a Bitcoin wallet, and everyone who sends any money to it gets a little something in return.

The only problem is that I have no way of confirming which person is behind every transaction. Is there an easy and surefire way for the senders to sort of "sign" their transactions, to be able to prove that it's theirs?

I don't understand why want to know the people behind the transaction which is simply not needed, all you should do is to send the bitcoins back to the address which sent the bitcoins to you and they will receive them in their wallets, its really simple i guess.

[OnkelPaul]

The safest way is to give each prospective funder a fresh address (and make a record of that bitcoin address and the info about the funder that you need to give them their "little something").
The addresses could be generated by a HD wallet, you will have to search a little to find something that fits into your crowdfunding infrastructure. Using a HD wallet has the advantage that you can generate the public keys (and addresses) from the public parent key, for example on the server with which your users interact, and keep the private parent key (and all the generated private child keys) safely out of reach of any hackers. Of course, if you use a HD wallet, you only store the key derivation paths for each funder, not the generated addresses, so you can compute the matching private key for each funder's address.

Do you think you can get this to work?

Onkel Paul

[MartinL]

I don't understand why want to know the people behind the transaction which is simply not needed, all you should do is to send the bitcoins back to the address which sent the bitcoins to you and they will receive them in their wallets, its really simple i guess.

Like he said: He is returning a brick and mortar service, not Bitcoins or any other digital asset.

[Kendji]

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.

It depends on what client you're using.  Basically, the sender just uses the address the coins were sent from to sign a statement proving to you who they are.  Then you use your client to verify that the message goes with the address.

Using core, here's what the sign message screen looks like:

That's awesome men

[Deep In The Mines LLC]

Get them to sign their transactions if you want them to prove it.

Or you can just send each person a unique address and reference the addresses with the person, that way you can know if they sent you the money or not.

[ethereumhunter]

You answered your own question actually... yes ask all senders to sign their sends.

Can you please tell me how it's done? I'm not very good at this, as you can probably tell.
-snip-

I guess the subtle hint was not enough.

CLICK HERE TO LEARN HOW TO SIGN A MESSAGE WITH VARIOUS WALLETS, HOW TO PRESENT THE MESSAGE TO OTHERS AND WHICH WALLETS DO NOT ALLOW YOU TO SIGN -> https://bitcointalk.org/index.php?topic=990345.0

i am visiting on the link you gave us and its really good for me to read about the sign in message in every wallet. actually i don't really too much about the sign in message, but after i read on your thread, i am learning something that maybe useful for me. thank you very much for your thread.

[arara]

In theory could be someone else with the private keys, but since I don't think people will hack private keys to send funds on behalf of other people, then I don't think it is a problem

just associate every person with an address