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Author Topic: Meetup question regarding double spends  (Read 875 times)
AgentofCoin
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February 27, 2016, 03:14:30 AM
 #21

...
Lol. I don't know anything anymore, but I think from the prior comments above of double-spending
(especially the definition knightdk provided me from the Bitcoin.org Developers glossary),
your definition of "spend" would not be correct as well. So I'm guessing there will be no consensus here, lol.

Even though in general I agree with your reasoning, I think the counter argument is as follows:
A "spend" is not when a tx has at least a single confirmation, but is any tx that is broadcasted.
This interpretation of "spend" does not change whether it is in a block or still pending in the mempool.

So according to this definition of "spend", it could really be considered a "push" and could be used interchangeably.
So in Bitcoin, when we are talking about "double-spending", we really mean "double-pushing", but call it "double-spending" anyway.

Lol.
Smile...No consensus?  But, it's just a minor semantic technicality!

I can understand the lack of consensus here because I can imagine a scenario such as this:  I participate in a Meetup at a local coffee shop, carry the tab for the group, transmit the transaction with the very minimal transaction fee, wait around for awhile for the delayed transaction, and then leave before it's confirmed.  While I'm out, I then somehow rebroadcast that same coin to myself with a much higher transaction fee.  I did receive the coffee and donuts for the transaction, so that situation would technically qualify as a "spend" although the transaction I broadcast to myself ended up receiving the first confirmations. Therefore, that would have to qualify as "double spend" by your understanding. Right?

I think I getting too confused now.

Originally, I assumed the term "double-spend" was for the duplication of a coin, and was comparable to the Bitcoin definition of "double-spend".
But no, according to common Bitcoin understanding, a "double-spend" is "a transaction that spends the same input as spent in another transaction."

So now I say, what is the definition of a "spend"?

If your version is correct, then the common understanding of the Bitcoin's definition of "double-spend" is wrong.
Since respectable members of the community say that a "double-spend" is "a transaction that spends the same input as spent in another transaction",
then the terminology of the word "spend" must be read in that context, thus a "spend" is really just a push or a broadcast.

Even though I think the term "spend" should convey that a tx was confirmed, it seems it does not.
And even though I would think the term "spend" would also convey a transfer of goods (coffee), it does not.

Basically, since terms are used loosely, a "spend" could also be interchangeably used with "push" and "broadcast".

Thus, a Bitcoin "double-spend" could also be called a "double-push" or a "double-broadcast", in theory.

Have I gone off the deep end here?  Huh

Edit: fixed redundant - not doesn't


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cjmoles
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February 27, 2016, 06:01:35 AM
 #22

...
Lol. I don't know anything anymore, but I think from the prior comments above of double-spending
(especially the definition knightdk provided me from the Bitcoin.org Developers glossary),
your definition of "spend" would not be correct as well. So I'm guessing there will be no consensus here, lol.

Even though in general I agree with your reasoning, I think the counter argument is as follows:
A "spend" is not when a tx has at least a single confirmation, but is any tx that is broadcasted.
This interpretation of "spend" does not change whether it is in a block or still pending in the mempool.

So according to this definition of "spend", it could really be considered a "push" and could be used interchangeably.
So in Bitcoin, when we are talking about "double-spending", we really mean "double-pushing", but call it "double-spending" anyway.

Lol.
Smile...No consensus?  But, it's just a minor semantic technicality!

I can understand the lack of consensus here because I can imagine a scenario such as this:  I participate in a Meetup at a local coffee shop, carry the tab for the group, transmit the transaction with the very minimal transaction fee, wait around for awhile for the delayed transaction, and then leave before it's confirmed.  While I'm out, I then somehow rebroadcast that same coin to myself with a much higher transaction fee.  I did receive the coffee and donuts for the transaction, so that situation would technically qualify as a "spend" although the transaction I broadcast to myself ended up receiving the first confirmations. Therefore, that would have to qualify as "double spend" by your understanding. Right?

I think I getting too confused now.

Originally, I assumed the term "double-spend" was for the duplication of a coin, and was comparable to the Bitcoin definition of "double-spend".
But no, according to common Bitcoin understanding, a "double-spend" is "a transaction that spends the same input as spent in another transaction."

So now I say, what is the definition of a "spend"?

If your version is correct, then the common understanding of the Bitcoin's definition of "double-spend" is wrong.
Since respectable members of the community say that a "double-spend" is "a transaction that spends the same input as spent in another transaction",
then the terminology of the word "spend" must be read in that context, thus a "spend" is really just a push or a broadcast.

Even though I think the term "spend" should convey that a tx was confirmed, it seems it does not.
And even though I would think the term "spend" would also convey a transfer of goods (coffee), it does not.

Basically, since terms are used loosely, a "spend" could also be interchangeably used with "push" and "broadcast".

Thus, a Bitcoin "double-spend" could also be called a "double-push" or a "double-broadcast", in theory.

Have I gone off the deep end here?  Huh

Edit: fixed redundant - not doesn't



LOL

Nah, I don't think you've gone off the deep end.

"Double spends," such as the "double spends" Satoshi pondered, are not possible because Satoshi created the block chain ledger which eliminated that problem.  However, the semantics of the "double spend" we're pondering in this thread is a whole different beast!  In reality, double spends, in the Satoshi sense, are not possible because only one transaction can be published in the ledger per input.  So, we can try to "double spend" in as many clever ways as we can hack out, but the ledger has the final word. The fact that the community agrees that the ledger is truthful and contains all known bitcoin transactions, leads to the following logic:

             If bitcoin double spends were a reality, they'd be included within the ledger.
             There are no double spends included within the ledger.
             Therefore, bitcoin double spends are not a reality.

So, the "double spend" we're talking about in this thread is a ghost of sorts because there is no such beast on the ledger.  Do we have consensus?

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February 27, 2016, 06:44:28 AM
 #23

Why does everyone make the answer to simple questions so difficult?

Double-spending is the result of successfully spending some money more than once. Bitcoin protects against double spending by verifying each transaction added to the block chain to ensure that the inputs for the transaction had not previously already been spent.

Other electronic systems prevent double-spending by having a master authoritative source that follows business rules for authorizing each transaction. Bitcoin uses a decentralized system, where a consensus among nodes following the same protocol is substituted for a central authority.

Bitcoin has some exposure to fraudulent double-spending when a transaction is first made, with less and less risk as a transaction gains confirmations.

https://en.bitcoin.it/wiki/Double-spending

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February 27, 2016, 06:59:48 AM
 #24

The main thing here is, ordinary transactions and newbies will not be able to double spend, and the odd occasion when it happened during a hard fork, it still meant nothing. The longest chain will

eventually take over and the double spend cancelled... right? We have no need to panic about double spends and merchants can feel safe, that once a confirmation has been received, no double

spends will be possible. As a rule, I would wait for at least 4 - 8 confirmations on bigger amounts before I accept the tx as being validated. {Yes, It's overkill, but it works} 

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