Topic: URGENT Transaction disappeared from blockchain in 12 hours (Read 2896 times)

Whow! That was well explained. I'm gonna +rep you just for writing this.

It happened like this:

On 2016-02-02 at 22:55:03 UTC the person that controls the private key for Bitcoin Address 1Mo1hzhZYDLuRJw5qrCnirmPerj3xBARH2 received a payment of 0.11244979 BTC in transaction b94df458bcf5fc1057709a741398d3699740283e5e1208a73c30337ffa4d41c5

They then created two unconfirmed transactions that BOTH attempted to spend this same 0.11244979 BTC.

One of them was transaction 6847504c014e6937410ac3d02f7693e10dae2ef4743d02a3d4883f65464936d8 which was broadcast and then received by blocktrail.com on 2016-02-02 at 22:56:40 UTC. This transaction attempted to create an output transferring 0.12040425 BTC to address 1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz, but it never confirmed.

The other was transaction 97a8a0d4426de5f1bc9299a6dd70eed32b1d4f2a91916166dcf4cd2bb4370d02 which was broadcast and then received by blockchain.info nearly 21 hours later on 2016-02-03 at 19:32:07 UTC.  This transaction transferred the bitcoins to address 1L4yNyudTekbCzyJ1FKU3FG9wm3aboWBhd and was confirmed in block 396540 on 2016-02-03 at 20:51:36.  Once this transaction became confirmed, the earlier transaction became invalid and was removed from all wallets that heard about the earlier transaction first and then received block 396540.

The first transaction remained unconfirmed until the second transaction confirmed.  Then the first transaction became invalid, and the output that it created for 1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz therefore ceased to exist.

While the first transaction was still unconfirmed, the person that controls the private key for address 1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz spent the unconfirmed 0.12040425 BTC output in transaction a17ec9679829650b308738b8dc8f3230de48d26fc59baaedda3da5dda6d7b940 which was seen by blocktrail.com on 2016-02-03 at 04:39:13 UTC. When the unconfirmed output later became invalid, this transaction and all of its outputs became invalid (A transaction is not allowed to spend an invalid output).

While it was still unconfirmed and not yet invalid, the person that controls the private key for address 1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz then spent an unconfirmed output from that transaction in a new transaction ( 5c807b50378eaa6f91c08d9961a6a7ccbb434f8a2985899310adb337b803395b ) which was seen by blocktrail.com on 2016-02-03 at 04:44:11 UTC. When the unconfirmed output later became invalid, this transaction and all of its outputs became invalid.

While it was still unconfirmed and not yet invalid, the person that controls the private key for address 1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz then spent an unconfirmed output from that transaction in a new transaction ( 0efe72bd6b0f31260c47ea222c3a6216a29e233ff7814019669f2d120a8e5fb9 ) which was seen by blocktrail.com on 2016-02-03 at 04:46:22 UTC. When the unconfirmed output later became invalid, this transaction and all of its outputs became invalid.

While it was still unconfirmed and not yet invalid, the person that controls the private key for address 1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz then spent an unconfirmed output from that transaction in the transaction that they sent to you ( 0efe72bd6b0f31260c47ea222c3a6216a29e233ff7814019669f2d120a8e5fb9 ) which was seen by blocktrail.com on 2016-02-03 at 04:46:22 UTC. When the unconfirmed output later became invalid, this transaction and its outputs to you became invalid.



This is why confirmations exist.  If a transaction confirms, then it is extremely unlikely that it will become invalid.  As the transaction gains more confirmations, the odds that it will become invalid decrease exponentially.  After 1 confirmation, you can feel comfortable that the transaction will remain valid.  A re-org could happen, but it isn't very likely.  After a few confirmations, you can feel confident that the transaction will remain valid.  A re-org isn't likely to happen unless there is either a malicious miner with control of nearly 50% of the global hash power or a bug that results in a significant fork of the chain.  After a few days of confirmation you can feel certain that the transaction will remain valid. A re-org isn't likely to happen unless there is either a malicious miner with control of significantly more than 50% of the global hash power or a bug that results in a disasterous fork of the chain.

If you spend or accept unconfirmed outputs, then there is a risk that a competing transaction will confirm and your transaction will become invalid.  If you are willing to take this risk, you can work with unconfirmed transactions, if you are not willing to take the risk, then you should always wait for confirmation.

I don't know, but it isn't related to this. This issue is specifically about Bitcoin, not blockchain.info. It is essentially about the protocol and how Bitcoin transactions work. The double spending is something in Bitcoin, not blockchain.info.

Then why do you think blockchain updated its wallet ? when I tried to login, it said v3 version is not supported . I was compelled to login through the beta version . Also I have updated my wallet on android .

Someone else is not actually controlling his account. blockchain.info didn't do anything wrong this time, this is just something that is a part of Bitcoin. This is why people usually tell you to wait for a few confirmations before accepting a payment and this is why most wallets will not allow you to spend from an unconfirmed input.

How can someone literally control any guy's account ? If someone can it would be really scary. Blockchain has upgraded their wallet and hope everything should be fine from now on.

Yes, essentially.

Look through the transaction history of the transaction. On blocktrail, there is a red arrow that points to the previous transaction referenced by an input. If the transaction is a double spend, it will tell you. Just keep going up the chain until you reach confirmed transactions. A transaction cannot be double spent if it is confirmed.

does that mean if there is double spend i a chain other tx will never be confirmed and the btc got stolen ?
there were more transaction done.
How can i check if there is double spent.

Whoever controlled https://www.blocktrail.com/BTC/address/1Mo1hzhZYDLuRJw5qrCnirmPerj3xBARH2 decided to double spend and they were successful. People spent off of that unconfirmed transaction (which is a terrible idea, case in point) and that resulted in your transaction ending up in that chain and thus when the double spend confirmed, the entire transaction chain became invalid.

How did this happened ?

Please do not double post, you posted this in new thread, don't do that.

The reason you see two different balances is because blocktrail is including an unconfirmed transaction in the calculation. Blockchain.info does not, probably because they dropped the transaction. As Danny said, different services can choose to do whatever they want with their nodes, and blockchain.info has decided to drop that transaction while blocktrail has not.

Your transaction will never confirm because farther up in the transaction chain is an unconfirmed double spend transaction. This transaction: https://www.blocktrail.com/BTC/tx/6847504c014e6937410ac3d02f7693e10dae2ef4743d02a3d4883f65464936d8 is a double spend of https://www.blocktrail.com/BTC/tx/97a8a0d4426de5f1bc9299a6dd70eed32b1d4f2a91916166dcf4cd2bb4370d02. Since the second transaction is confirmed, the first one which your transaction depends on is now invalid. Therefore any transactions based on that first transaction (which includes yours) will never become confirmed because they are now invalid.

try to look at this post:
https://bitcointalksearch.org/topic/m.13766424

this wallet has $50
https://www.blocktrail.com/BTC/address/14vrdrwsNJK3AdnerLWVwq2PSSZJcJVqGq

but blockchain shows
$1.16
https://blockchain.info/address/14vrdrwsNJK3AdnerLWVwq2PSSZJcJVqGq

If is was a valid transaction in the first place, then it was unconfirmed.  It has now been removed from the memory pool from most peers.  This can for any of the following reasons:

• Enough time has passed and most wallets have decided to make room in RAM for more recent transactions
• The transaction to you became invalid because the outputs that were used as inputs to fund the transaction to you were confirmed as inputs for some other transaction that sent that value elsewherep
• The transaction to you became invalid because the outputs that were used as inputs to fund the transaction to you were unconfirmed and became invalid

Unless there has been a huge chain re-org that I'm not aware of, it would have to have been unconfirmed.


An unconfirmed transaction is a transaction that is not yet in THE BLOCKCHAIN.  The website that is run by a company that calls themselves blockchain.info might have shown the transaction, but they have a reputation for showing inaccurate information sometimes.  Additionally, when they show unconfirmed transactions, they can vanish at any time.  While it frequently takes 2 to 3 days for their servers to choose to drop unconfirmed transactions, there is no requirement for them to wait that long.  If the transaction becomes invalid they could drop it immediately.  If they decide that the transaction isn't likely to ever confirm they could drop it immediately.  It's there website, they can show whatever they like.


Nope.  A "multiple-spend attack" can be instant.  As soon as one of the competing transactions confirm, the rest of the transactions are invalid and most wallets will immediately drop the competing transactions.  If someone was successful in an attack against the person that sent you bitcoins, then the bitcoins they tried to send to you might have vanished from their wallet before the transaction to you could confirm.

I want to know one thing.
https://www.blocktrail.com/BTC/address/1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz/transactions
https://blockchain.info/address/1FX4fnxikvhhK3cSxiuX9MkRPqpLJAr6Hz

why blockchain is showing less transaction than blocktrail of this address

In that case, I don't have an explanation. Once a tx is confirmed, it should be impossible to "disappear".
Maybe someone smarter than me can help you.

but double spent take 2-3 days to disappear from blockchain

What if the sender double spent the inputs he used for your transaction? Would blockchain.info show an error or just remove the faulty tx?

When this transaction was made i did not checked whether it was confirmed or not.
But an unconfirmed transcation takes 2-3 days to disappear from blockchain.
But this transaction was made 12 hours ago and now its gone.

Strange... I'm using my phone ATM, but I don't see any transaction between those 2 addresses (I might be overlooking it).
Any idear if the transaction had confirmations?

this is my address
    14vrdrwsNJK3AdnerLWVwq2PSSZJcJVqGq