From: ZmnSCPxj <ZmnSCPxj@protonmail•com>
To: Adam Gibson <ekaggata@gmail•com>,
Bitcoin Protocol Discussion
<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] bustapay BIP :: a practical sender/receiver coinjoin protocol
Date: Wed, 30 Jan 2019 08:34:46 +0000 [thread overview]
Message-ID: <q_EImVoLLoTdTZI0kPb4olI3FFjIMx9Uj0O8acFefNbsMtU7K25wWz69Alm-jbwZ8SEV1U3Y6Re3705Xi2zQb5129MbtjEVE8dT_JtSSfmA=@protonmail.com> (raw)
In-Reply-To: <226c43d8-1fad-9d90-ba47-9230118e447d@gmail.com>
Good morning Adam,
> And I'm reminded that a related point is made by belcher in the gist
> comment thread iirc (after we discussed it on IRC): over time a
> "PayJoin-only" merchant doing the simplest thing - using a single utxo
> over and over again, will concentrate more and more funds into it, and
> inevitably violating UIH2 in an increasingly dramatic fashion
> (contributing a 100BTC utxo to a 0.1BTC payment etc.). Suggesting it's
> better if there's a mix of payjoin/non-payjoin.
To be pedantic: as I understand bustapay, it would still not violate UIH2 (unless I misunderstand UIH2).
Suppose the original transaction is: (0.05 payer, 0.07 payer) -> (0.1 payee, 0.02 payer)
Then bustapay with such a PayJoin-only merchant with 100BTC UTXO would give: (100 payee, 0.05 payer, 0.07 payer) -> (100.1 payee, 0.02 payer).
As I understand it, this technically does not violate UIH2.
It would still conceivably be interpreted as a payment of 100.1 BTC, from a payer who happens to have massively lopsided UTXOs being owned, but still does not violate UIH2.
However, if that 100.1 UTXO is subsequently used to pay a 100.3 payment, then that is used to pay a 100.7 payment, that strongly suggests such a naive PayJoin-only merchant.
Perhaps a simple heuristic against this would be:
1. For every UTXO you own, flip a coin.
If all of them come up heads, do not payjoin; just broadcast the original transaction.
2. Else, randomly select a UTXO (value not care?) and payjoin with that UTXO.
However, I have no proper analysis of the blockchain, so --
Regards,
ZmnSCPxj
prev parent reply other threads:[~2019-01-30 8:34 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 20:24 rhavar
2018-09-10 12:30 ` Sjors Provoost
2018-09-10 15:49 ` rhavar
2019-01-25 14:47 ` Adam Gibson
2019-01-27 7:36 ` rhavar
2019-01-27 12:20 ` Adam Gibson
2019-01-27 19:24 ` rhavar
2019-01-27 19:42 ` James MacWhyte
2019-01-27 22:11 ` rhavar
2019-01-30 2:06 ` James MacWhyte
2019-01-30 2:46 ` rhavar
2019-01-30 20:58 ` James MacWhyte
2019-01-28 4:14 ` ZmnSCPxj
2019-01-28 13:19 ` Adam Gibson
2019-01-30 8:34 ` ZmnSCPxj [this message]
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