Hello ZmnSCPxj,

Thanks for your response.

The spending tx of multisig can be decided earlier and all three can review the 
outputs involved in it. All 3 txs involved in the system if we consider only 
one mixer and not a chain will get confirmed in the same block as we are using 
CPFP so child pays for 2 parent txs. However, disputes are possible and to 
manage it we will have to make the system complex with things like Peer 1 
locking some amount in a 2 of 2 multisig with Peer 2 or some other incentives 
structure. Initially we can try to keep it simple and a way to spend coins 
after coinjoin with the help of another person you trust.
Yes, you described coinjoin in joinmarket but the problem I am trying to solve 
is: spend coins after coinjoin because post-mix usage is as important as 
coinjoin. Some users dont follow the best practices after coinjoin and it makes 
coinjoin useless or less effective in that case and sometimes for others 
involved in the process as well.
Samourai has few options for users to do this and one of them is: Stonewallx2 
which is a mini coinjoin and similar to what I was trying with this idea.
End goal is to create more options for users to spend UTXOs easily in different 
ways after coinjoin which makes it difficult for people trying to analyze 
transactions or algorithms monitoring, flagging, reporting txs 24/7
Its just an idea for now and maybe I might find better ways to solve this 
problem once I start working on it. For me it makes sense to experiment with 
things and provide more options for users but I wanted to see what others think 
about it who are more experienced and skilled to develop bitcoin related 
Thanks for this link: https://zmnscpxj.github.io/offchain/generalized.html 

Looks interesting.

May 26, 2020, 08:16 by zmnsc...@protonmail.com:

> Good morning Prayank,
>> 1. Peer 1 doesn't need to be a trusted third party, it can be implemented in 
>> a way that some peers involved in this system can provide liquidity for 
>> others and incentives can be a small fee.
> It is not clear in the article, but you mention using a 2-of-3, and show 3 
> participants.
> It seems to me that Peer 1 and Peer 3 (2-of-3) can simply sign to spend the 
> funds coming from Peer 2, and split the funds of Peer 2 among them, without 
> getting input from Peer 2.
> That is the reason why I consider this tr\*sted --- Peer 2 has to trust Peer 
> 1 does not collude with Peer 3 to steal the funds of Peer 2.
> Unless I have misunderstood your article, which is why I asked for 
> clarification.
>> 2. Yes joinmarket is awesome and its payjoin will be better to achieve the 
>> same but I was trying to contribute and add more options for people to 
>> improve privacy on Bitcoin. If we have different ways to mix it will be 
>> harder for spy companies to analyze of some of the transactions.
> * While JoinMarket has *a* PayJoin implementation, what I described in the 
> previous email was not a PayJoin, it is standard CoinJoin where one of the 
> equal-valued outputs is to the payee.
>  * In particular, PayJoin requires the cooperation of the payee, what I 
> described does *not* require anything from the payee other than a destination 
> address and an amount to pay.
> * Your described technique (as I understand it) is not too different from 
> what JoinMarket already does for normal sends, with the JoinMarket technique 
> having the advantage that it works with the current paradigm of "send payment 
> to this address" without reconnecting to the payee.
>  The advantage you describe is largely had only if the technique is 
> significantly different.
>  For instance, CoinSwap and CoinJoinXT are different enough from CoinJoin to 
> be valuable in this respect.
>> 3. Also one such setup might not make a huge difference but a chain of such 
>> mixers will surely work better if everything done correctly. 
>> 4. Maybe multisig usage is not ideal for such things right now and I am not 
>> the best person when it comes to coding but think that better privacy for 
>> multisig will make it possible for lot of ideas to be implemented on Bitcoin 
>> using different multisig setups and combination of other things that we 
>> already have.
> Schnorr (which is introduced as a package deal with Taproot) already makes 
> all n-of-n look the same as 1-of-1 without tr\*sted setup, and makes hidden 
> m-of-n possible with some kind of setup (possibly untrusted I think, but I am 
> not enough of a mathist to describe this, in any case my base understanding 
> is that the setup for m-of-n Schnorr requires a complex ritual involving a 
> number of communication rounds).
> Taproot allows to hide explicit m-of-n in a script behind some kind of n-of-n 
> or m-of-m.
> So multisignature usage would automatically gain such advantage once Taproot 
> gets deployed.
> In any case, if you are still interested in protocol design with some amount 
> of focus on privacy, please consider reading this article as well: 
> https://zmnscpxj.github.io/offchain/generalized.html
> What exactly is your goal here.
> Regards,
> ZmnSCPxj

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