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Here's a payjoin demo, so people have some idea what workflow might be like: joinmarket.me/blog/blog/payjoi

(used asciinema + tmux, quite a nice combination btw!)

@waxwing Not sure if it's something of interest for joinmarket but here's something that I posted last week on the other site.

It's a steganographic 2-party coinjoin (third tx on the schema). Basically, it's what you get when you mix coinjoin and P2EP ideas :D

The scheme has some nice properties (hides paid amount, breaks basic assumptions about ownership of output changes)

@laurentmt

Yeah these are all very reasonable possibilities :) Reminds me of that example I gave in Milan where I said there were at least 8 interpretations :)

Nice work, thanks. (btw the pic comes out twice for some reason).

@waxwing First pic shows 3 similar coinjoins. Second pic has labels showing who controls which UTXO, depending on the Stonewall option used in Samourai Wallet (from top to bottom: Stonewall, Stonewall-2P, Steganographic Stonewall-2P).

@laurentmt Oh the labels! I focused really hard to check that the amounts were really the same and so were the descriptions; didn't notice the labels :) Figured it out though :)

@stevenroose @waxwing Yep. It could be interpreted as BA->ABBA (among others interpretations).

But the real interpretation is that both mixed outputs go to one participant and both change outputs go to the other participant. It breaks the classic assumption that each participant is associated to 1 mixed output and 1 change output.

@laurentmt @stevenroose

I like to call this the "coinjoin hall of mirrors" :) One interpretation is the "obviously correct" one, so those trying to gain privacy deliberately use the less-accepted pattern; then the analyst notices most people are using the "not obvious" pattern, so it becomes the accepted interpretation, and then ... :)

@waxwing @laurentmt That's why we have things like canonical input and output ordering, right.

@stevenroose @laurentmt

Well it's certainly related but: ordering has no semantics in theory (also Gmax has elucidated good reasoning as to why *if anything* bip69 is not a good thing, although it doesn't matter too much); so interpretation is really all about amounts and utxo relationship (clustering, address reuse etc.).

@waxwing @laurentmt I don't see how it is a bad thing.
If course, it'd be better if it had set the guideline that wallets just have to randomize order instead of defining an order.

@stevenroose @laurentmt
SIGHASH_SINGLE is a corner case where it *could* be a bad thing (although no one really uses it right now). I forget, but I think there were one or two other counterarguments, but anyway as I said, it's not like it's terrible. Randomization might indeed be the better way to go.

@waxwing
Is it just me or does it not play correctly?
Viewing it online, the right part of the pane isn't visible, neither in default size or maximized.

If I download the .cast file and view it with asciinema (thx for the tip!), then I can see it all, but depending on the window size, some columns from the right pane are displayed on the left (and then it continues on the right).

It plays correctly if I have my Konsole window maximized :)

asciinema has a cat command \o/

@FreePietje Oh! I didn't think to check this; viewing it at the given asciinema linnk, on a wide monitor it looked good here; but maybe if you reduce the size on the browser (like ctrl -) it might show up properly?

Kind of surprised because I recorded it on a small laptop screen with default font in the terminal, I guessed it shoud be fine.

@FreePietje I think it might be "just you" 😆 because I tried it on two different monitors (small and large) and asked a couple of other people, they said it was fine to. Maybe it's the browser you're using?

@waxwing
Wouldn't be the first time 😂

I'm using it on Firefox and the issue is that the player is hosted in a pane and Ctl+- changes the player size and the contents in it, thus has not the desired effect.
My monitor is 1920x1080

@waxwing
Just testing it with Chromium (Debian) and there it does display correctly

@FreePietje Well this is weird.

On my machine my setup is also 1920x1080, firefox, and it's Ubuntu. And it looks as intended; the player screen is like twice as wide as it is tall (approx). Confirmed that ctrl - is irrelevant.

No idea what's different for you.

@waxwing
I don't know either. Anyway, I can see it in all its glory :)

FTR: Chromium version 72.0.3626.53
Firefox versions 60.4.0esr and 64.0

Attached screenshot of maximized window

@FreePietje Sorry it's screwed up for you.

64.0 FF here also; tried on two machines, one a laptop screen, another a 2 monitor setup. Seems to make no difference. One other person said they had no issue either.

@waxwing
Don't worry about it :)
I now have multiple ways to watch it as intended. And I learned about asciinema, which really is cool as well.

I wasn't kidding when I said "Wouldn't be the first time 😂 "
I just mentioned it in case there was an issue for others as well.

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