Is it at all possible to associate an IP address with a Bitcoin address?

[gigabytecoin]

If you don't send your coins to/from an IP obviously

Say you generated a block of 50 coins (ie. didn't buy them anywhere, no trail yet) and then spent them from your machine later to purchase something you didn't want anybody to know about. Or the funds just happen to go to an unscrupulous individual in general and when he cashes them out them somebody wants to speak to you (the person who funded him) for some reason or another let's say.

Could somebody tell simply by looking at the block chain or other factors what ip address sent or generated what coins?

I know messages can be sent with blocks. Is any information related to the owner's computer stored at all in the block chain basically is my question?

[titeuf_87]

Blocks and the transactions included in them don't contain any IP addresses.

Transactions do contain your public key(s), so if you keep your bitcoin addresses private (and never reuse them), it is a lot harder to find out that those transactions come from you.

Keep in mind that the bitcoin client combines smaller transactions in bigger ones. If you have one of those transactions linked to you, then it shows that all the other transactions are also yours.

[bitlotto]

In the blockchain - no

If I was trying to track you down I'd try to get blockexplorer.com's logs. Then see if that address was ever looked up without TOR or a proxy. If so, I'd see who owns that IP address. If a proxy was used I'd see what other addresses were looked up at a similar time from that proxy IP address and see what those other Bitcoin addresses visitors looked like. I could then assume and link a few bitcoin addresses to that other address and hope they visited one without a proxy...but it wouldn't always work...

[joan]

Another approach would be a "node-id attack" where the attacker would somehow control your neighboring nodes in the P2P overlay.
This way the attacker can distinguish between transactions you created vs transactions you are merely routing.
This can be achieved by exploiting the server responsible for the mapping of nodes.

(No sure if such an attack is possible on Bitcoin, you can decide to bypass the irc channel and only connect to trusted nodes)

[Anonanon]

I wouldn't want my IP address in anyway linked to any Bitcoin addresses.

[gigabytecoin]

I wouldn't want my IP address in anyway linked to any Bitcoin addresses.

You and me both, brother!