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150 sats \ 3 replies \ @nout 1 Jun 2022 \ on: A List of Proposed Bitcoin Privacy Improvements | sethforprivacy.com bitcoin
Great summary on important topic :) I hope to see more posts like this... and that's why I boosted some sats your way ;)
- There's this ring signature proposal for Bitcoin, but not sure if anything ever came out of that: https://sci-hub.se/10.1109/CIS.2017.00075
- And here seems to be some update for Stealth Addresses: https://sci-hub.se/10.1109/ICCCWorkshops49972.2020.9209929 (again I have no idea about quality of this paper)
Seth, are you planning on keeping this article up to date?
The ring signature proposal:
The idea is by no means dumb but from my somewhat brief reading (then again, it's a somewhat brief paper, to say the least!), I don't see a materially important difference to the Chaumian blinding construction.
In both cases, you start by submitting your inputs (the paper unhelpfully uses the term 'transactions' for input utxos). In this new idea you also submit an ephemeral public key and then once the server sends back a list of all participant public keys, and it's this set of keys you form ring sigs over, that is, you ring-sign each of your destination addresses.
To do that without trivially linking inputs to outputs (which is the desirable property with a server-based mix, for privacy from central coordinator), you're going to need to break the network linkage between the first and second phase. This is exactly the same as when using Chaum blind signatures.
It is also a shame that the paper does not discuss ring signature properties in any detail. Its definition of the term does not discuss the crucial property of spontaneity, nor linkability (which is important in Monero but I guess not, here), nor culpability, which could well be relevant in potential DOS attacks against this construction.
So TLDR it's interesting but probably not revolutionary, and the paper is really lacking in detail.
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On second thoughts I guess you do need the 'linkability' property as in Monero, because you don't want someone double-signing, that is, for input A, you don't want them to be able to submit an output set of address and amounts twice. But ...
this is where the lack of detail matters. Is it intended for construction equal-amount coinjoins? It seems like that's tacitly implied, and that the output address set that each participant sends is supposed to add up to some fixed amount. That's a whole can of worms already (see Wabisabi). And/or: what about change outputs? Depending on the model those could be sent along with the inputs, or over separate network identities.
TLDR this is just a vague idea, not a proposal, I think.
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Seth, are you planning on keeping this article up to date?
Absolutely, it's not easy to keep things like this up to date but I will try my best. All of the source for the site/posts is on Github as well, so pull requests to correct/keep things up to date are always welcome! The specific source for this post is here:
There's this ring signature proposal for Bitcoin
Will give it a read and add if it makes sense, thanks!
And here seems to be some update for Stealth Addresses
Will give it a read as well and share with Monero researchers to see how relevant it may be, thanks! Had definitely not seen this before, though.
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