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From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
To: Dmitry Petukhov <dp@simplexum.com>
Cc: "bitcoin-dev@lists.linuxfoundation.org"
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] SAS: Succinct Atomic Swap
Date: Wed, 03 Jun 2020 14:36:46 +0000	[thread overview]
Message-ID: <UumGKofzr_d8aqpQE2fS6kkbJTRfkuOwpbdNBlaNLe8hB_pUZSI0kNOypT-HeSsQP3ZXoW4vyvknUyQ6Zi22rDLGcedvkv_Rj6pgVbNVKUM=@protonmail.com> (raw)
In-Reply-To: <20200603140425.2a4e9d60@simplexum.com>

Good morning Dmitry,

> I made a version of the TLA+ spec according to the suggested variant,
> as I understood it from your description. This version is in
> the separate branch in the SASwap repo, 'variant_ZmnSCPxj' [1]
>
> If I understood and specified your variant correctly, there is a
> deadlock possible after step 9, if Bob fails to publish success tx in
> time. After refund tx becomes spendable, Alice cannot publish it via
> mempool, because Bob can learn her secret and has a chance invalidate
> her refund tx by giving his success tx to friendly miner, while taking
> back the locked LTC because both secrets are known. At the same time,
> Bob cannot publish success tx via mempool, because then Alice can do
> the same thing, invalidating his success tx with refund tx via friednly
> miner.

Indeed, this is precisely the issue Ruben pointed out.

Rationally, neither side will want this condition due to the deadlock and Bob will strive to avoid this, having a short real-world timeout after which Bob will force publication of the success tx if Alice does not respond in time.
There *is* a reason why it says "Bob claims the BTC funding txo before L1."

Of course, computers do crash occasionally, I am informed, so complete accidents may occur that way.
This can be mitigated by running multiple servers who are given copies of the success tx, and which will publish it regardless after a short sidereal time duration, unless countermanded by the main server (i,e, a dead man switch system).
With sufficient distribution the probability of this occurring can drop to negligible levels compared to other theoretical attacks.

Regards,
ZmnSCPxj



  reply	other threads:[~2020-06-03 14:36 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-11 15:29 [bitcoin-dev] SAS: Succinct Atomic Swap Ruben Somsen
2020-05-11 16:45 ` ZmnSCPxj
2020-05-11 17:50   ` Ruben Somsen
2020-05-12  4:41     ` ZmnSCPxj
2020-06-03  9:04       ` Dmitry Petukhov
2020-06-03 14:36         ` ZmnSCPxj [this message]
2020-05-12 22:50     ` Chris Belcher
2020-05-12  6:10 ` Lloyd Fournier
2020-05-12  6:50   ` Lloyd Fournier
2020-05-12 11:30     ` Ruben Somsen
2020-05-12 11:34       ` Ruben Somsen
2020-05-12 15:05       ` ZmnSCPxj
2020-05-12 16:30         ` Ruben Somsen
2020-05-13  8:39           ` ZmnSCPxj
2020-05-13  9:57             ` Ruben Somsen
2020-05-13  9:58               ` Ruben Somsen
2020-05-13 11:39                 ` ZmnSCPxj
2020-05-13 12:33                   ` Ruben Somsen
2020-05-15  4:39                     ` ZmnSCPxj
2020-05-15 19:47                       ` Ruben Somsen

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