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There are several (in my view unnecessary) default limits carried over from core which weaken zeroconf. The unconfirmed ancestors limit for example. These kinds of limits become quasi-consensus, and especially in the case that implementations differ, it creates a simple doublespend vector. The lowest hanging fruit in improving zeroconf is removing limits, or making them officially consensus rules so we can be certain all implementations are deploying them consistently.
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   10mo ago
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Couldn't most of the merchant risk associated with instant transactions be solved by using a very well connected SPV wallet with low/no defaults? The SPV would use a sliding scale wait time based on the transaction amount. i.e. wait longer for larger value transactions from a few seconds for very small value transactions up to n conformations for large value txns if necessary. SPV would relay a reject back to the merchant for any instant transactions that spends the same output.
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   10mo ago
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@MJahnz SPV wallets by design limit their view of the Bitcoin system to only the part that they are interested in. Which means that they only see transactions that use the addresses the SPV wallet is interested in.
For this reason the double spend transaction that pays the thief back his own money will not be seen by the merchants SPV wallet. Because none of the addresses from the SPV wallet are used in that transaction.
As such, an SPV wallet is currently mostly blind to double-spend attempts. The only solution that solves this for SPV we know of are double-spend-proofs.
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   10mo ago
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@TomZ Apologies I meant to say SPV service. e.g. a merchant would run an SPV wallet that connects to and SPV service. The SPV service would be very well connected and monitor all transactions for double spends. Does Flowee expect to be very well connected and does it have the potential to monitor all txns for double spends?
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   10mo ago
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Thanks for the followup, sorry for the slow reply @mjahnz
Yes, Flowee intends to cater to that audience. The point with a double spend proof is that the full node doesn't have to be well connected. There no longer is a reason to.
That said, yes, Flowee intends to be well connected. But there will always be a larger risk that double spends are not seen that way than with the proofs.
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   9mo ago