Proving you own a bitcoin address

[anu]

From my understanding, if you have some coins on a virgin Bitcoin address, the public key is a secret. Until you transfer money from that address, at which point the public key is known to the network.

So owning the public key of a virgin address should constitute proof that you also own the private key?

[JoelKatz]

Say you show me the public key to an account to prove to me it's yours. Now I can show that public key to anyone to prove it's mine. But it's not mine. So this can't be right.

[drakahn]

You could sign a message with the address

[FreeMoney]

You should sign the message with the private key. Virgin, not, doesn't matter.

[Stephen Gornick]

You should sign the message with the private key. Virgin, not, doesn't matter.

And if the OP wasn't aware, this feature is built into the Bitoin-qt client.

[anu]

You should sign the message with the private key. Virgin, not, doesn't matter.

And if the OP wasn't aware, this feature is built into the Bitoin-qt client.

Ah, the signmessage and verifymessage command. Excellent. Many thanks!

[niko]

From my understanding, if you have some coins on a virgin Bitcoin address, the public key is a secret. Until you transfer money from that address, at which point the public key is known to the network.

So owning the public key of a virgin address should constitute proof that you also own the private key?

How can you have any coins on a virgin address? How did they get there?

[JoelKatz]

How can you have any coins on a virgin address? How did they get there?

Someone sent them to you, of course. But since you've never spent any of them, your public key has never been disclosed.

[niko]

How can you have any coins on a virgin address? How did they get there?

Someone sent them to you, of course. But since you've never spent any of them, your public key has never been disclosed.

Sorry, but I still don't get it. Isn't the receiving address in the blockchain?

[JoelKatz]

Sorry, but I still don't get it. Isn't the receiving address in the blockchain?

Yes, but we're talking about the public key. That's only placed in the blockchain when it's used to claim a transaction output. If you've never spent any coins, your public key will normally not be in the blockchain no matter how many coins have been sent to you. All that's known is your address (a hash of the public key).