Knowing a single transaction can you track down a Bitcoin user?

Question

I have used this transaction to donate to Wikileaks. I have applied no special techniques to obsure my identity. How much information can find out about me on the blockchain. What tools would you use?

Can you guess the following information? Can you prove it?

• How did I get the bitcoins I was donating?
• What else did I use my bitcoins for?
• What was my total bitcoin balance at a given time?
• What wallet am I using?

Please try not to violate other people's right to privacy.

Answer 1

• Knowing the Wikileaks donation address, one knows every address that contributed to them.
• Knowing a given address we are interested in, we can try tracing the coins back to when they were created (which can be harder if they were mined by a large pool, in that case you'd probably get a lot of origin blocks).
• Given an address we know when it received coins and from what address.
• If the particular wallet contained more than one receiving address, sometimes the addresses would be used together. If you have more than one address in the "From address", you know the person had to have them together in on wallet.

And now a bit of knowledge one can gain from outside the Block Chain:

• A lot of people put notes like "My Bitcoin Address is: 1HWbVLhxj7bhewhyapMZpyhqWAeAhJd51E" in places like the forum. Then you can link the addresses to particular nicknames, and in some cases emails, names, facebook pages and so forth. If you use one address for everything, one can know if you contributed to Wikileaks, or other known addresses.
• If one would have a big node in the Bitcoin Network that by chance would be connected to your Client when it sends transactions using the known addresses, one could potentially trace the IP of your computer. If you have a static IP, this can identify you.

So all in all, with enough resources, time and determination, one can know quite a lot about a given Bitcoin address. A lot of it can be mitigated with enough diligence, but some of methods might be quite hard.

Answer 2

You can use the 'Address balance sheet' tool at http://blockchain.info/address-balance-sheet and add the addresses associated with the transaction whose owner you are trying to identify.

For example for the transaction you mentioned most common ip is 109.201.253.77 from Dnepropetrovsk, Ukrane. It is not always accurate but if you have enough addresses patterns can emerge, is this correct?

Answer 3

Addresses can be grouped as belonging to the same user (or, better, same "account") by grouping together the addresses that participate as inputs to a single transaction, and doing it transitively. This has been done in the recent paper by Shamir and Ron, by some previous researchers and can be done by znort's parser. This is not 100 % accurate since it is possible for different users to sign different inputs to the same transaction, but currently people don't do that very often. (But this may change in the future.)

Using this method, the above-mentioned research determined that certain bitcointalk users donated to WikiLeaks just from their self-published donation addresses (event though they might not have used the same addresses for the donations).

For doing this analysis, one doesn't even necessarily need to know a transaction you created, it might be enough to know just one of your public addresses.

Se also this question.