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From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
To: Chris Belcher <belcher@riseup.net>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Improving JoinMarket's resistance to sybil attacks using fidelity bonds
Date: Tue, 06 Aug 2019 02:54:14 +0000	[thread overview]
Message-ID: <vwdvU8vMocIk6rEm5jdlRa9G_0dsDyNjURYYxin6HcjDddDFv8IyOQcxNvnGn6ywFLVWkVb7VvP-qcboH1EX8f_t85sbyuCzT6DbXhj5if0=@protonmail.com> (raw)
In-Reply-To: <ad501873-8912-765e-8df5-c9b0451fcd0a@riseup.net>

Good morning Chris,


> This could be worked around by honest makers because they
> can consolidate TXOs on the blockchain, which rented TXO owners can't do
> because the TXOs are owned by different people.

Would it not be possible the below?

* I rent some funds from Dmitry.
  I agree to pay him 0.5 BTC for this service of putting up 50BTC from Dmitry UTXO.
* I also own 50BTC myself in a separate UTXO.
* We create a funding transaction paying out to a Schnorr MuSig output that is 2-of-2 between us.
  This spends Dmitry UTXO 50 BTC and my UTXO 50BTC.
  We only create this yet and do not sign.
* We create a backout transaction, probably with `nLockTime`, paying out 50.5BTC to Dmitry and 49.5BTC to me.
  This spends the funding transaction.
  We sign this using MuSig.
* After we exchange the signatures of the backout transaction, we exchange signatures for the funding transaction.
* Now we have a common 100BTC UTXO (indistinguishable from other Schnorr single-sig UTXOs) that can be used as fidelity bond for me.
  This is the output of the funding transaction.

The above can be scaled up so I can rent arbitrary amounts of coin from many different people, who are assured of getting their funds back, in exchange for a fidelity bond / advertisement, and thus greatly destroying the properties of the V^2 tweak.

(The ability to have shared ownership of UTXOs is a powerful feature of Bitcoin, and backs its ability to scale, as witnessed with Lightning Network and channel factories.)

Regards,
ZmnSCPxj


  parent reply	other threads:[~2019-08-06  2:54 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-25 11:47 [bitcoin-dev] Improving JoinMarket's resistance to sybil attacks using fidelity bonds Chris Belcher
2019-07-26  8:10 ` Tamas Blummer
2019-07-26  9:38   ` Dmitry Petukhov
2019-07-30 21:39     ` Chris Belcher
2019-07-31 15:50       ` Dmitry Petukhov
2019-08-02  9:21         ` Chris Belcher
     [not found]           ` <20190802145057.7b81c597@simplexum.com>
2019-08-05 19:04             ` Chris Belcher
2019-08-06  1:51               ` Leo Wandersleb
2019-08-06 10:27                 ` Chris Belcher
2019-08-06 13:07                   ` Leo Wandersleb
2019-08-06  2:54               ` ZmnSCPxj [this message]
2019-08-06 20:55               ` Dmitry Petukhov
2019-08-06 21:37                 ` Dmitry Petukhov
2019-08-06 23:33                   ` ZmnSCPxj
2019-08-07  9:38                     ` Chris Belcher
2019-08-07 11:20                       ` ZmnSCPxj
2019-08-07 10:05                   ` Chris Belcher
2019-08-07 11:35                     ` ZmnSCPxj
2019-08-07 15:10                     ` Dmitry Petukhov
2019-08-08  0:09                       ` ZmnSCPxj
2019-08-08  9:35                         ` ZmnSCPxj
2019-08-08 11:37                           ` Dmitry Petukhov
2019-08-08 13:59                             ` ZmnSCPxj
2019-08-08 20:06                               ` Chris Belcher
2019-08-08 12:05                       ` Dmitry Petukhov
2019-07-27 19:34 ` David A. Harding
2019-07-28 14:17   ` Tamas Blummer
2019-07-28 18:29   ` Tamas Blummer
2019-07-30 21:27   ` Chris Belcher
2019-07-31 17:59     ` David A. Harding
2019-08-02 14:24 ` Adam Gibson

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