A few minutes ago I received 0.00000001 BTC. I don't know who sent them or why.

But what makes it crazy is, this sum was sent to an address I do not own and which the client I'm running (the standard Bitcoin-QT, versione 0.8.5) had never heard of before. I know this for sure because I only created 2 (two) addresses using this client, and the receiving address of this transaction is not one of them.

How is this possible at all?
Is it a hash collision, or what else?

The address is 1Cz2AmLe8U52KR549d13JQkqsqkV64RchB and the transaction ID is b9591410ff030e40deb3eda9d2fe30a29642ede443f354bb5f4ed5bb55f0d36d.

According to this page, the address seems to have received money a little time before from 1HTawQNCS4axPXft6L6fkzrv5ya7TguqwD, which actually is one of my addresses; the last two transactions are me sending all my BTCs to a new address, just to be sure. This worked, so it looks like I'm actually the owner of that address, even if my client doesn't list it as one of mine.

What's exactly going on here?

  • Are you involved in a mining pool? You may have received a proportion for your work
    – Patrick
    Commented Oct 15, 2013 at 10:33
  • I actually am, but the pool doesn't make such small payouts. And still the main question remains... I don't own that address!
    – Massimo
    Commented Oct 15, 2013 at 10:35
  • Satoshi was clever. Change addresses add an extra layer of anonymity. The bitcoin-qt wallet GUI doesn't have any indication that they exist, however. This might be for simplicity's sake.
    – bvpx
    Commented Oct 15, 2013 at 15:40
  • Yes, Satoshi was clever, but you mean "anonymity" with quotes. It's possible to trace money in Bitcoin with a reasonable confidence level. Commented Oct 15, 2013 at 15:51

3 Answers 3


As Murch says one possibility is that this address is in your keypool. Another is that this is a change address the client created. If you're willing to share the relevant transaction we may have more to say.

Owning an address means "being in unique possession of a corresponding private key". It's difficult to know if you're the only owner, but verifying you have a key is easy - ask bitcoin-qt to sign a message with this address.

  • Question updated. And yes, it looks like that address actually belongs to me...
    – Massimo
    Commented Oct 15, 2013 at 11:03
  • Ok, I've looked up change addresses (en.bitcoin.it/wiki/Change), and it looks like it's one of them, and it's normal to not see it in the client GUI. But why did I suddenly receive 0.00000001 BTC on it? Who sent them and why?
    – Massimo
    Commented Oct 15, 2013 at 12:03
  • 1
    Never heard of that service before... and the change address was created only a couple of hours before receiving that satoshi. Also, I received ANOTHER satoshi from the same address on the new address I started using soon after. Maybe someone is sending satoshis to any new address it sees on the blockchain?!? I'm puzzled.
    – Massimo
    Commented Oct 15, 2013 at 16:15
  • 1
    @Massimo: Some people do weird things. Commented Oct 16, 2013 at 5:34
  • 3
    @Massimo: Actually, this tx is probably an advertisement. Note that there's also a public note on blockchain.info advertising their site. Commented Oct 16, 2013 at 5:37

Bitcoin-qt has always at least 100 unused addresses in store. You probably received the payment to one of those.

If it were a hash collision that would very disconcerting, it might indicate that there is also trouble with the randomness in the standard libraries used by bitcoin-qt.

  • But even if this is the case, I don't know them and never told them to anyone...
    – Massimo
    Commented Oct 15, 2013 at 11:03

Check if that address appeared on the blockchain before that mystery payment. If it does, they could have gotten it from there. Also if you used it as a change address for a payment to someone, maybe you overpaid and they are refunding your overpayment (possibly in an automated process)

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