[SOLVED] Bitcoin sent to an additional address I didn't choose

[airconditioning]

(problem and solution summed up in last post of the thread)
Hi,


My experience with Bitcoin is rather limited : I thought the idea was interesting, bought about 5 bitcoins one year ago and let them sit in my bitcoin core wallet (I had 4.9 bitcoins yesterday). Since my network is often slow, it is not very practical for me to run a bitcoin node and I often take time to catch up to the network when I start the application, so I decided to move my bitcoins from one wallet to another (Electrum) when installing a new version of my Linux distribution (mint 18).

I decided to send 0.1 bitcoin first to see if everything went smoothly (I'm really glad I did), now I see two problems (see screenshots below for more details) :
1) incredible fee amount : on Electrum I see 0.15 bitcoin fee for 0.1 bitcoin transfer in the transaction, so a total of 0.25 bitcoin. There should be a big red popup in bitcoin core "You're about to transfer the equivalent ~125USD but it is going to cost you ~315USD because of ridiculous fees", seriously.
2) According to my Bitcoin node with bitcoin core and a blockchain, my receiving address on my old distro still has 4.8 bitcoins, as if the whole transaction cost ~0.1 bitcoin, not ~0.25. Electrum says 0.1 transfer + 0.15 fees and that is also what Bitref says.

A. I don't understand why my bitcoin core node would not be aware of those fees when it is completely synced with the network and aware of the 0.1 transaction itself? (the transaction is confirmed now)
B. Those fees are crazy (and I didn't run the slider to fast transaction), when I simulate sending back ~0.08 bitcoin on Electrum, it says fee should be around ~0.0003 bitcoin. In my mind Bitcoin just went from "potential alternative to banks" to "potential scam". So if I wanted to send the 4.6 remaining bitcoins, should I first buy ~7 additional bitcoins to pay the fees? If not how much is expected for such a transaction at a normal speed of confirmation?

Does anyone understand those two issues?

I hope I did not make any english mistake but I'm not a native speaker, so I apologize if I did.

[airconditioning]

I noticed something more : the transfer in bitcoin core is listed as :
-0.10004500 BTC
So I'm guessing bitcoin core did its job and added 0.000045 BTC of fee for the transfer of 0.1 BTC. So where do the 0.15 BTC fee come from?

I used to mine a little about two years ago, I never solved a block but I read some documentation back then and it was written nowhere that miners could just decide fees by myself and "extort" BTC on their own. How is that possible? Since my own node diffused on the network 0.1 transfer and 0.000045 fees? Can other nodes just overrun what you send if they stay longer on the network/are more numerous?

[airconditioning]

Ok, I noticed 2 new things :
1) Looking at the details in bitcoin core ,I was right : the fees were 0.000045 BTC, with the same transaction number (see screenshot)

2) If you look back at the BitRef.com screenshot in my first post, you can see that the total amount 0.100045 + 0.149755. is exactly equal to 0.2498, which is the same amount I first sent to this address about one year ago (but sent instead of received this time).
I suppose it could be a simple bug but I do not know or own the 1Hat... address so I think it looks like something malicious.

As if somehow the additional amount to reach 0.2498 BTC was added to my own 0.100045, but to a different address.

I am wondering now : should I leave my node running to inform other nodes the transaction was only 0.1 BTC, or since there is apparently a way to send some of my bitcoins to other addresses in transactions would there be a risk for the remaining 4.6 BTC to be transferred as well? (which wouldn't make much sense since I run this node once in a while to catch up to the network, so if my node was corrupted I guess those bitcoins could have been transferred a while ago)

I run bitcoin-0.12.1.

May a moderator move this thread in the security or scamming forum please?

[bitkilo]

Please post the transaction txid's to make it easier for people to help look into this for you.
The fees on the network have increased not anywhere near that much so something is not right.

I would advise you to keep your coins in the address you know they are save at till we work this out.
I will have a look myself when back online in a few hours.

[airconditioning]

Great, thanks

Here is the transaction ID :
fd8e703ab90b3c8819d4999999b8be907ff3866356c6e57f5c3a21672c6f9328-000

Here is the address on my Electrum wallet for the transaction :
13J2dUYSDZBRKN2eTmCLQT1f6t7iWwFr92

Here is the unknown address which got ~0.15 BTC for no apparent reason, but doesn't appear in my bitcoin core node transaction log (see screenshot of third post) :
1HatmU7DbbnBv69BKMJu8bHHdCcQD5NkFN

[bitkilo]

The address 1HatmU7DbbnBv69BKMJu8bHHdCcQD5NkFN is a change address of yours from the transaction and would belong in your core wallet, you may have to remember sync your wallet to see it appear.

[airconditioning]

Thank you That would explain why it complemented a previous amount, if it was received on one address so everything was sent from this address.

It doesn't appear in my sending or receiving addresses though. I'm syncing right now and will confirm as soon as I can but there is no block source available right now so this might take two three hours.

[airconditioning]

Thank you Bitkilo You were right. It is a change address.

I confirmed it by typing listaddressgroupings in the bitcoin-qt console window.

To sum it up for someone else who would have the problem later :
- after sending 0.1 bitcoin to myself I noticed another address I didn't know received 0.15 bitcoin
- it turns out it is a change address, because bitcoin handle "virtual money" by blocks
- I had a "block" of 0.2498 BTC, I sent 0.1 to my Electrum wallet, there was 0.1498 that bitcoin-qt sent to a new address from a pool, a change address that is in my bitcoin-qt wallet
Read about those change addresses if you don't know them as it can affect how/how often you backup your wallet.