Similar to this question, for which I think it is not clear enough, I'm interested when a transaction is considered practically confirmed. My question is:

What metric is used to measure transaction confirmation confidence in a scenario where the coordinator will be offline?

The reason why I think the linked question does not answer my question properly is that it talks about a rule of thumb that reminds me of the example given in the whitepaper (select 100 random tips and see if they reference your transaction). What bothers me is:

Why 100 random nodes? Why not a 1000? Who and why set the metric? Is it similar to 6 blocks in BTC or 12 in ETH (that is, just a rule of thumb)?

  • Please clarify what information you deem missing in ben's answer on the linked question. Furthermore, those four questions are vastly different and an SE question should focus on one question. – Helmar Jan 4 '18 at 11:54
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    I have edited the question to be more specific, emphasizing the issue that bothers me most. – user3223162 Jan 4 '18 at 13:02

If λ is the average rate at which transactions are issued in the tangle, then the cumulative weight of any single transaction (i.e. the count of transactions that directly & indirectly reference that single transaction) is expected to behave as follows,

enter image description here

where up until the Cut the growth is exponential, and linear thereafter with slope λ. One could argue that once the cumulative weight has ventured significantly into the linear zone (i.e. has thoroughly been embedded into the tangle) and is thus indirectly referenced by almost all newly-issued transactions, then your transaction is "confirmed".

  • Although generally a great explanation, I would like to see some numbers. Do you have any insight how already existent services determine whether a transaction is confirmed or not? Do they rely on the coordinator? – user3223162 Jan 4 '18 at 13:50
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    @user3223162 Unfortunately, I don't know what each service does (probably variants of looking at coordinator & this 100 random selection method). But you could create a separate question asking how the IOTA wallet specifically determines confirmed transactions. – Phil-ZXX Jan 4 '18 at 14:24
  • Thank you for your answer, I have pursued the issue further in iota.stackexchange.com/questions/1160/… – user3223162 Jan 4 '18 at 14:49

The number of path to check is indeed arbitrary. The idea is that you must check enough paths so that the estimation of portion of tips approving your transaction is accurate.

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