1
When seeing transactions I see that the number of confirmations keeps increasing without any limit.
I wanted to know if there is any time limit on including a already confirmed transaction in a block by a miner. Like transactions not older than a year, etc.
2
A "confirmation" is merely how many blocks that are after the confirmed transaction in the blockchain plus the transaction's block itself.
For example, if a transaction is in block 5,000, and there are now 5,005 blocks then that transaction has 6 confirmations.
Can you please elaborate? The same transaction should have been included in those 5 blocks to say that the transaction has 5 confirmations. If suppose, that transaction was included in only 2 blocks after the initial confirmation, then that transaction will have 3 confirmations. Am I right? – zak – 2014-07-22T14:16:40.423
@zakir No, a transaction, defined as a spent output, can only appear once in the blockchain. "Confirmation" here doesn't mean what one would expect it to mean. It's jargon for "number of blocks after a transaction's block". It doesn't mean "how many people have said 'yes, it's in here'". It's simply a bad misnomer. – None – 2014-07-22T14:31:51.280
1Actually, "number of blocks after a transaction's block" does mean "how many people have said 'yes, it's in here'". Each block contains a (merkle root) hash of its transactions, and a hash of the previous block. The chain of blocks following a transaction all confirm that the transaction happened, although the transaction is only explicitly included in the one block (this may be what @Cincinnatus meant). There's no way for future blocks to "leave out" (i.e. not say 'yes, it's in here') the transaction unless they try to build a block from the chain before the transaction was ever included. – Tim S. – 2014-07-22T15:16:14.687
@TimS. Now, don't go shooting holes through my misclarification of a misnomer. ;)) I meant that a node doesn't simply ask for a yay/nay response from another node if a transaction's block has been properly added to the blockchain, which would be far less secure than getting deeper in a locally confirmed PoW merkle chain, as you say. It surely wouldn't take 60 minutes to get 6 of those. – None – 2014-07-22T15:29:23.390
1Yep, yep...good to clarify that we don't trust an easy, simple yay/nay response, we trust blocks (which is basically a yay/nay, but with a proof of a huge amount of work). – Tim S. – 2014-07-22T15:36:50.127
Actually, if the transaction is in block 5000 and there are now 5005 blocks, it has 6 confirmations (1 confirmation from being in block 5000 + 5 more confirmations). – Biteasy.com – 2014-07-23T06:52:20.090