Date: Wed, 24 Oct 2018 18:21:00 +0000
To: Gregory Maxwell <greg@xiph.org>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: rhavar@protonmail.com
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Subject: Re: [bitcoin-dev] Transaction Input/Output Sorting
Precedence: list

Actually, I think it can be calculated a bit smarter using maths (which unf=
ortunately I'm not very good at...). But I assume it's something like:

```
falsePositiveChances :=3D 0.0

foreach( transaction of transactions) {
=09falsePositiveChances +=3D (1 / factorial(transaction.Inputs)) * (1 / fac=
torial(transaction.Ouputs))
}

totalFalsePositives :=3D falsePositiveChances / transactions.length
```

If so, I get 42.4% false positive rate. So clearly bip69 is getting used a =
fair bit, but not nearly as much as randomization.


-Ryan

=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original Me=
ssage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
On Wednesday, October 24, 2018 10:52 AM, <rhavar@protonmail.com> wrote:

> That's pretty easy to quantify. I wrote a quick script to grab the last f=
ew blocks, and then shuffle the inputs/outputs before testing if each trans=
action is bip69 or not.
>
> The result was 42% of all transactions would accidentally be bip69 when r=
andomized.
>
> So clearly randomization is a lot more popular than bip69 at the moment, =
but I'm not sure that it matters much. As soon as you have more than a few =
inputs/outputs, you can tell with a high confidence if the transaction is b=
ip69 or not.
>
> And of course if you're clustering a wallet, you can figure out extremely=
 easily how that wallet behaves wrt bip6.
>
> -Ryan
>
> =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original =
Message =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
> On Wednesday, October 24, 2018 9:12 AM, Gregory Maxwell via bitcoin-dev b=
itcoin-dev@lists.linuxfoundation.org wrote:
>
> > On Wed, Oct 24, 2018 at 3:52 PM Chris Belcher via bitcoin-dev
> > bitcoin-dev@lists.linuxfoundation.org wrote:
> >
> > > Thanks for bringing our attention to this important topic.
> > > According to (https://p2sh.info/dashboard/db/bip-69-stats) around 60%=
 of
> > > transaction follow bip69 (possibly just by chance).
> >
> > A two input randomly ordered transaction has a 50% chance of
> > 'following' bip-69. So 60% sound like a small minority.