Transaction sent back to sender How could this possibly be???

[kcsunshine]

Can someone please explain what happened here exactly please? The below transaction was initiated with a fee per of 143 satoshis per byte, and it is showing unspent on the blockchain, but apparently the sender said that it came back to him. How could this possibly be???


txid
https://blockchain.info/tx/996520ceda3521cc1ca410a70d81bda6fa214413b8922ea0592e60f45db7be84?show_adv=true


address
https://blockchain.info/address/13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk

[kahc]

Can someone please explain what happened here exactly please? The below transaction was initiated with a fee per of 143 satoshis per byte, and it is showing unspent on the blockchain, but apparently the sender said that it came back to him. How could this possibly be???


txid
https://blockchain.info/tx/996520ceda3521cc1ca410a70d81bda6fa214413b8922ea0592e60f45db7be84?show_adv=true


address
https://blockchain.info/address/13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk

As seen here https://blockchain.info/address/1GRGJdVCv3nFoUHgducFwiVsUWzmfz864E , he double-spend to another address(3Q1FLQFfbsXsF4VfPjwYkbHhfxLSaqxjRA) with a higher fee.

So the transaction to your address 13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk will soon disappear or be marked as "double-spend".

[kcsunshine]

Can someone please explain what happened here exactly please? The below transaction was initiated with a fee per of 143 satoshis per byte, and it is showing unspent on the blockchain, but apparently the sender said that it came back to him. How could this possibly be???


txid
https://blockchain.info/tx/996520ceda3521cc1ca410a70d81bda6fa214413b8922ea0592e60f45db7be84?show_adv=true


address
https://blockchain.info/address/13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk

As seen here https://blockchain.info/address/1GRGJdVCv3nFoUHgducFwiVsUWzmfz864E , he double-spend to another address(3Q1FLQFfbsXsF4VfPjwYkbHhfxLSaqxjRA) with a higher fee.

So the transaction to your address 13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk will soon disappear or be marked as "double-spend".

When someone is sending me bitcoin then, how do I detect a double spend before the transaction to me is confirmed??


UPDATE:


Wait a minute. The transaction you show there that is confirmed, happened a day later. So I ask again (please no offense), How is it that the first transaction I show was sent back please. Look at the dates.

[Thirdspace]

When someone is sending me bitcoin then, how do I detect a double spend before the transaction to me is confirmed??

by NOT acknowledging the transaction UNLESS it has received certain number of confirmations
some exchanges or services only credit user deposit after 3 or 6 confirmations for safety
in another words... you should never proceed your business before you are sure the tx is confirmed
even with 1 confirmation it could turn unconfirmed if it was rejected by the rest nodes on the main chain

Wait a minute. The transaction you show there that is confirmed, happened a day later. So I ask again (please no offense), How is it that the first transaction I show was sent back please. Look at the dates.

exactly... it is confirmed a day later while the earlier tx never got confirmation at all
so the latter tx is consider valid after a few confirmations and the earlier will be dropped and treated as invalid
its not about which one was sent out first but which one is confirmed first and accepted by majority nodes

[kcsunshine]

When someone is sending me bitcoin then, how do I detect a double spend before the transaction to me is confirmed??

by NOT acknowledging the transaction UNLESS it has received certain number of confirmations
some exchanges or services only credit user deposit after 3 or 6 confirmations for safety
in another words... you should never proceed your business before you are sure the tx is confirmed
even with 1 confirmation it could turn unconfirmed if it was rejected by the rest nodes on the main chain

Wait a minute. The transaction you show there that is confirmed, happened a day later. So I ask again (please no offense), How is it that the first transaction I show was sent back please. Look at the dates.

exactly... it is confirmed a day later while the earlier tx never got confirmation at all
so the latter tx is consider valid after a few confirmations and the earlier will be dropped and treated as invalid
its not about which one was sent out first but which one is confirmed first and accepted by majority nodes

WOW!!

So I do I detect from the beggining that a user is trying to rip me off??? How do I know he didn't send those funds to two wallets at the same time or something??? I need to know this because Ido a lot of bitcoin transactions.

[kahc]

When someone is sending me bitcoin then, how do I detect a double spend before the transaction to me is confirmed??

by NOT acknowledging the transaction UNLESS it has received certain number of confirmations
some exchanges or services only credit user deposit after 3 or 6 confirmations for safety
in another words... you should never proceed your business before you are sure the tx is confirmed
even with 1 confirmation it could turn unconfirmed if it was rejected by the rest nodes on the main chain

Wait a minute. The transaction you show there that is confirmed, happened a day later. So I ask again (please no offense), How is it that the first transaction I show was sent back please. Look at the dates.

exactly... it is confirmed a day later while the earlier tx never got confirmation at all
so the latter tx is consider valid after a few confirmations and the earlier will be dropped and treated as invalid
its not about which one was sent out first but which one is confirmed first and accepted by majority nodes

WOW!!

So I do I detect from the beggining that a user is trying to rip me off??? How do I know he didn't send those funds to two wallets at the same time or something??? I need to know this because Ido a lot of bitcoin transactions.

To detect a double spend attack while the transaction has 0 confirmation. You have to check the network for additional transactions with the same unspent transaction output that can be spent as an input in a new transaction.


To prevent falling for double spend attack.
Wait for at least 1 confirmation before you finalize your trade, and the risk of double-spending is statistically zero.
Always be aware if someone sends you a transaction with suspiciously low fee.(which will probably never confirms)

[LoyceV]

So the transaction to your address 13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk will soon disappear or be marked as "double-spend".

It's not even a double spend, it was never spend to TS.
If it's a double spend, blockchain.info shows a big warning. Now it shows this:

Note the negative Final Balance.

Blockchain.info has bugs: it is possible to create "transactions" that only show up on blockchain.info. I've seen it before. I don't know how they do it, it seems they only broadcast it to blockchain.info and not to other nodes. This typically shows a negative balance on the address, which obviously shouldn't be possible.
If you try to find the transaction in any other block explorer, it doesn't exist.
I don't know why blockchain.info doesn't fix this, it's abused by scammers a lot.

So I do I detect from the beggining that a user is trying to rip me off??? How do I know he didn't send those funds to two wallets at the same time or something??? I need to know this because Ido a lot of bitcoin transactions.

This scam could have been seen by checking another block explorer, or probably your own wallet too. I'm pretty sure this one didn't show up in your own wallet yet.
Satoshi recommends to wait for 6 confirmations before trusting a transaction. Unless you're dealing with very high amounts, I'd take 1 confirmation as enough.

[kcsunshine]

So the transaction to your address 13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk will soon disappear or be marked as "double-spend".

It's not even a double spend, it was never spend to TS.
If it's a double spend, blockchain.info shows a big warning. Now it shows this:
https://s18.postimg.org/daus8sk21/gif.gif
Note the negative Final Balance.

Blockchain.info has bugs: it is possible to create "transactions" that only show up on blockchain.info. I've seen it before. I don't know how they do it, it seems they only broadcast it to blockchain.info and not to other nodes. This typically shows a negative balance on the address, which obviously shouldn't be possible.
If you try to find the transaction in any other block explorer, it doesn't exist.
I don't know why blockchain.info doesn't fix this, it's abused by scammers a lot.

So I do I detect from the beggining that a user is trying to rip me off??? How do I know he didn't send those funds to two wallets at the same time or something??? I need to know this because Ido a lot of bitcoin transactions.

This scam could have been seen by checking another block explorer, or probably your own wallet too. I'm pretty sure this one didn't show up in your own wallet yet.
Satoshi recommends to wait for 6 confirmations before trusting a transaction. Unless you're dealing with very high amounts, I'd take 1 confirmation as enough.

Very interesting.

To provide insite to this thread, I will add that the transaction was sent from a coinomi wallet, and if I am correct, they use shapeshift. Scary. Lesson learned here. Use more than one block explorer to check tx.

This transaction looked perfectly normal  especially right after it was transmitted, because the negative balance did not show up until the next day!!! One would have assumed that this would have eventually confirmed, but it was never going to!!!

If you have anymore comments as to what i added it would be appreciated, and thanks for your valuable input.

[LoyceV]

To provide insite to this thread, I will add that the transaction was sent from a coinomi wallet, and if I am correct, they use shapeshift.

How did this happen exactly? Was it someone at your house, showing you his wallet? I've heard about fake banking apps (in the Netherlands), used to pretend to pay someone when buying goods. A fake Bitcoin app would be new to me.

This transaction looked perfectly normal  especially right after it was transmitted, because the negative balance did not show up until the next day!!!

The negative balance on blockchain.info only happened when they made the second payment (the real payment).

One would have assumed that this would have eventually confirmed, but it was never going to!!!

With the current high fees I wouldn't assume it confirms before it's dropped from mempool. I have an outgoing unconfirmed transaction for 3 days now, I'm curious to see if it gets dropped (in which case I'll rebroadcast it) or that it just stays unconfirmed until it confirms.

[kahc]

So the transaction to your address 13Y46QiUbbqEZhHWgHdHUJpt8PrEfz8qTk will soon disappear or be marked as "double-spend".

It's not even a double spend, it was never spend to TS.
If it's a double spend, blockchain.info shows a big warning. Now it shows this:
https://s18.postimg.org/daus8sk21/gif.gif
Note the negative Final Balance.

Blockchain's algorithm of detecting double spend is not perfect, they can't detect every double spend.
I assume in this case is because of more than 24 hours between the 1st and 2nd transaction.

The sender clearly made a transaction with the same unspent transaction output as input in a new transaction.
If not double spend, what do you call this?

[kcsunshine]

To provide insite to this thread, I will add that the transaction was sent from a coinomi wallet, and if I am correct, they use shapeshift.

How did this happen exactly? Was it someone at your house, showing you his wallet? I've heard about fake banking apps (in the Netherlands), used to pretend to pay someone when buying goods. A fake Bitcoin app would be new to me.

This transaction looked perfectly normal  especially right after it was transmitted, because the negative balance did not show up until the next day!!!

The negative balance on blockchain.info only happened when they made the second payment (the real payment).

One would have assumed that this would have eventually confirmed, but it was never going to!!!

With the current high fees I wouldn't assume it confirms before it's dropped from mempool. I have an outgoing unconfirmed transaction for 3 days now, I'm curious to see if it gets dropped (in which case I'll rebroadcast it) or that it just stays unconfirmed until it confirms.

It's a friend. He claims that he initiated the transaction from his coinomi wallet and that all of a sudden the funds appeared back in his wallet for some reason, and then he tried to send them out to a different address. to be clear, i did not get ripped off, and the only reason that I am wondering about this, is because I have never seen this before. I buy a lot of btc from strangers, and once i see the transaction coming, i check the fee, make sure it's unspent, and then i pay them without the tx getting confirmed. In this case I would have been burnt.


The second payment registers a day later. It is still unexplained why the funds came back, and as someone stated here as well, the first tx only shows up on blockchain.info. It no longer shows on any other block explorer and may never have, not sure.

[Thirdspace]

this explorer might give you a hint next time someone tries to trick you
https://bitaps.com/1GRGJdVCv3nFoUHgducFwiVsUWzmfz864E
https://bitaps.com/996520ceda3521cc1ca410a70d81bda6fa214413b8922ea0592e60f45db7be84
it has a double spent tag/status when there's 2 transactions using the same unspents
as others and I previously said... wait for at least 1 confirmation before proceeding the trade
and for bigger amount, it's recommended and a lot safer to wait for 3 or 6+ confirmations

[kahc]

this explorer might give you a hint next time someone tries to trick you
https://bitaps.com/1GRGJdVCv3nFoUHgducFwiVsUWzmfz864E
https://bitaps.com/996520ceda3521cc1ca410a70d81bda6fa214413b8922ea0592e60f45db7be84
it has a double spent tag/status when there's 2 transactions using the same unspents
as others and I previously said... wait for at least 1 confirmation before proceeding the trade
and for bigger amount, it's recommended and a lot safer to wait for 3 or 6+ confirmations

Thanks for reminding me of bitaps.
I was looking for that block explorer, but I kept searching "bitsap" on google and found nothing, so I thought they were discontinued.