January 29, 2020
<sarang> Let's go ahead and get started with GREETINGs
<RingSize937> v Greetings
<sarang> Let's continue with ROUNDTABLE, where anyone is welcome to share research topics of general interest (and discuss any questions arising from them)
<sarang> Since there was so much to discuss last week, I'll try to keep the discussion focused to the extent possible, for clarity
<sarang> I have a few brief things to mention
<sarang> First, I wanted to better understand the effects of including hidden timelocks in CLSAG signatures, and worked up a version of 3-CLSAG in C++ for performance tests
<sarang> Including timelocks would negate the verification time advantages of an MLSAG-CLSAG transition
<sarang> but would still give size benefits over MLSAG
<sarang> A similar approach would work in Triptych, so I extended the Triptych test code to 3-Triptych for this purpose
<sarang> And, just for completeness, updated the Triptych preprint on IACR to a general d-LRS construction
<sarang> Here is the 3-CLSAG test code, for those interested: https://github.com/SarangNoether/monero/commit/db33d18bb889043c4bdea6d8582ffe2f6c581d28
<sarang> And the 3-Triptych concept code: https://github.com/SarangNoether/skunkworks/commit/f7581a385d72baa3dbb60c83e8d856a9335bec1f
<sarang> And the updated Triptych preprint: https://eprint.iacr.org/2020/018
<sarang> I also found a very minor change to make in the existing CLSAG test code
<sarang> Finally, suraeNoether and I have been doing more security model stuff
<sarang> Any questions on these items from anyone?
<koe> not directly for sarang, but at Isthmus regarding timelock; what is the prevalence of non-zero timelock for non-coinbase tx?
<Isthmus> Absurdly prevelant
<koe> whether or not to include encrypted time lock depends in part on how much use it actually gets
<sarang> Yeah, and I'm not formally advocating for it at this point; only curious about the implications
<Isthmus> I think our options are to remove the silly timelock field (It's just an arbitrary integer memo field currently) or encrypt it.
<koe> I like that it's a straightforward application of concepts already used in Monero
<sarang> Yeah, conceptually it's really neat
<Isthmus> Will we be the first privacy coin to roll it out?
<Isthmus> I expect that it will become industry standard
<sarang> Does Zcash offer such functionality?
<sarang> (I have not checked)
<sgp_> no clue
<Isthmus> I don't think so, but not 100% confident
<ArticMine> ZCash has serious scaling issues
<sarang> Anyway, whether or not Zcash does it should not be the determining factor IMO :)
<sarang> Merely curious
<Isthmus> Oh wait. Zcash inherited nLockTime from Bitcoin
<Isthmus> I'mma fish out their information leaks too
<Isthmus> And OP_CLTV
<sarang> If implemented, it would make the most sense to bundle the timelock range proofs with the existing Bulletproofs
<sarang> So this means the sum of timelock-enabled inputs (all inputs, if mandatory) and outputs is restricted
<koe> for Triptych, what are the steps between now and considering it for replacing RingCT?
<sarang> Formal review, a determination about its effects on multisig (particularly on compute-limited hardware), a decision on Triptych vs something like RCT3
<sarang> I have not yet examined how easy it would be to include timelocks in RCT3 with their security model
<ArticMine> ^ … and estimated recommended tx size for Triptych
<sarang> Also note that, as I think I mentioned last week, it would not make sense to deploy hidden timelocks with MLSAG due to the poor scaling
<sarang> (though technically possible)
<sarang> Anyway, I want to make sure others have time to speak as well
<sarang> Who else wishes to share research topics?
<Isthmus> Zebra network stack looks interesting, potential applications in Monero?
<sarang> I saw that yesterday!
<sarang> Blag post about it: https://www.zfnd.org/blog/a-new-network-stack-for-zcash/
<sgp_> cool, will check out
<sarang> And a corresponding forum post (not much activity there yet): https://forum.zcashcommunity.com/t/a-new-network-stack-for-zcash/35870
<sarang> It's from Zcash Foundation research
<Isthmus> Monero maintains a single state across all the peers, right?
<sarang> That's a good question, and I don't know the answer
<sgp_> ping vtnerd
<sarang> I had thought so, but not confident in that
<hyc> not even sure what that means. single state? what is included in that state?
<hyc> there is an aggregate state for bandwidth limiting
<hyc> but sync info is per-connection
<Isthmus> Oh so maybe we already take the Zebra approach?
<Isthmus> It seems pretty elegant.
<sarang> Isthmus: did you have other topics you wanted to bring up as well?
<hyc> "Unlike zcashd, which maintains a fixed number of outbound connections, we attempt to connect to as many peers as possible, subject to resource limits "
<hyc> this approach will be troublesome for them, since they use levelDB/rocksDB for storage
<hyc> lvelDB/rocksDB requires thousands of file descriptors for its storage.
<hyc> that competes with the demand for socket descriptors
<sarang> Interesting… worth bringing up as a question on the forum?
<sarang> One of the developers (Henry) opened the thread
<hyc> not from me. I have no interest in helping zcash project
<Isthmus> I'm trying to make the unlock time plot, but my laptop is struggling with the 1.5 GB data set
<hyc> they should have already known by now that their DB choice is inappropriate for a network service that uses lots of connections, but it seems they haven't discovered that yet
<sarang> Isthmus: no rush!
<sarang> In the meantime, koe: did you wish to address anything in particular?
<koe> yes muahaha
<koe> not technically research, my roadmap has been cleaned up a bit; in particular I want to get opinions on item koe_11, which would enable view-only wallets to know when owned outputs have been spent; also item koe_9 which would allow all wallet implementations to more or less deprecate pre-RingCT transaction versions
<hyc> koe_11 sounds like a high priority
<koe> also, sarang helped me work up a decentralized CoinJoin-esque protocol (temporarily named JoinMo), which is available as chapter 9 of current ZtM2 draft
<koe> chapter 10*
<sarang> I like the JoinMo approach of using per-participant shared secrets to obscure the input-output mapping
<koe> also, rbrunner at one time investigated OpenBazaar integration, and ran into some roadblocks, so my 'research' has been engineering solutions to those problems, which should be available next week
<sarang> I'm giving extra scrutiny to the specifics around SAG/LSAG since the keys are per-output only
<sarang> I was thinking about the implications of using a separate keyset for inputs as well
<sarang> (keys = per-join participant keys, I mean)
<koe> however, OpenBazaar integration would likely entail a large update to the code-base, to optimize communication rounds
<koe> moreover, multisig in general should be updated to comply with suraeNoether's paper on the subject
<Isthmus> Somewhat related to item 10, I'm still concerned about any blockchain observer being able to identify which transactions do not include any outputs to subaddresses.
<Isthmus> n3ptune and I will make a plot of subaddress adoption over time : -)
<Isthmus> But ideally that should not be possible.3
<sarang> Also yes :)
<sarang> It's been suggested before to standardize on some form of per-output keys for this purpose
<sarang> but it never gained traction
<sgp_> koe: nice list! koe_9 may be controversial since spending pre-rct would stand out more, no?
<atoc> Yeah looks like a nice list koe
<koe> it already stands out like a sore thumb
<koe> but that sort of problem will exist for RingCT as well, since spending ancient outputs is always somewhat unusual
<koe> and my suggestion is to start using pre-ringct outputs as decoys as well
<hyc> If we told everyone to sweep them to themselves, would that also be too obvious? you could assume that every txn with pre-RCT inputs is going back to its sender
<koe> so gamma select over entire site of outputs
<sgp_> koe: do we currently only select rct randomly as decoys?
<koe> yes, and coinbase (not sure if pre-ringct coinbase are included)
<koe> coinbase are included as decoy in normal tx, which is where this idea comes from
<sgp_> then this actually makes spending pre-rct slightly less suspicious, no?
<sarang> And the handling of coinbase outputs is by no means solved
<Isthmus> This is 80% a joke: We implement Koe_9 and sgp_coinbase_only rings, *but* require each and every one to include N coinbases and M pre-ringCT transactions, for fixed consensus parameters N and M
<sarang> sgp_: the distribution tail falls fast
<sgp_> sarang: indeed, but it's near-zero better, not near-zero worse I think
<sarang> Yes, but does provide slightly more information (amount)
<Isthmus> ^ which is hilarious, because all of these would hypothetically unlock at HEIGHT 2 and HEIGHT 12 back in 2014, IIRC what mooo said
<sarang> Due to the non-standard handling of that field, you mean?
<sarang> (which should be standardized anyway)
<sgp_> Isthmus: hmm, I would need to see a lot more info on how many people actually spend pre-rct (suspected) compared to coinbase. My intuition leans no
<ArticMine> So include a single pre ring CT fake if the real output is not pre ring ct
<Isthmus> @sarang: Yes, currently, 3 things are being put in the unlock field:
<Isthmus> Argh sorry
<Isthmus> Small integers like "12", presumably to be interpreted as height differences, i.e. "unlock in 12 blocks"
<Isthmus> Large integers like "1980000", presumably to be interpreted as block heights
<Isthmus> Very large integers like "1578561720", presumably to be interpreted as unix timestamps
<atoc> I am working on a first version implementation of xmr-btc atomic swap in Rust
<atoc> more info here: https://github.com/h4sh3d/xmr-btc-atomic-swap/blob/master/whitepaper/xmr-btc.pdf
<sarang> atoc: did you identify a suitable zkp?
<sarang> Aside from things like the handling of non-compliant participants etc., the zkp of hash/log preimage was not specified
<atoc> the paper proposes two transactions for each token
<atoc> is there is a zkp not specified I will look at it. So far I have just gotten some initial stuff implemented
<atoc> however I have not gotten to the swap part yet
<atoc> for the implementation, I have read through the paper and it seems sounds
<sarang> Yeah, you'll notice there's a requirement for a particular proof that a hash preimage and discrete log preimage are equal in equal knowledge
<sarang> Something trustless like Bulletproofs could be used for this, with a suitable circuit
<atoc> I see
<sarang> The BP paper had data on such a circuit, but I was specifically told it was for testing only and was not yet suitable for any kind of deployment
<atoc> I will take a look at that
<atoc> We will need it. Perhaps we can see if that circuit works okay, and if not hopefully we can look at ways to improve.
<sarang> koe: thanks for that roadmap writeup; it's nice to see many suggestions put together in one place
<sarang> It might be useful to open research-lab issues for those that require ongoing discussion
<sgp_> I still advocate for those two mining pool-related proposals btw :)
<atoc> sarang I send you a link to my repo once I push some changes
<sarang> even though most discussion happens on IRC
<atoc> I will send*
<sarang> Thanks atoc
<atoc> You can take a look and I would like to get your feedback on it
<sarang> Happy to help
<sarang> Thanks for taking a look at that
<koe> sure I can put on research github; was just wondering if koe_11 should go on main repo's issues
<atoc> Np, it seems interesting. This week I was just l familiarizing myself with different atomic swap techniques i.e off-chain and on-chain
<atoc> And looking at the dalek library in Rust
<sarang> koe: I'd say anything that requires ongoing unsolved research is definitely suitable for research-lab
<sarang> But I don't dictate the scope of issues!
<sarang> OK, we have about 10 minutes left (there's another meeting taking place at 19:00 UTC for the Konferenco)
<koe> ok can put them up there
<sarang> Any research topics that have not yet been brought up, and should be?
<atoc> sarang btw have you considered publishing your list?
<sarang> Of topics I am personally working on? Not really, it's more to help organize my own work
<atoc> The private list that you had of research topics that need attention.
<sarang> I should open issues for them as well
<sarang> TBH github issues for research are not used as well as they could be
<atoc> Yeah I think it would be could to have a public list to look through as important topics for Monero that need attention
<sarang> Since so much of the discussion happens on IRC in real time
<atoc> yes indeed
<sarang> But at least those issues could be used as a central posting location
<atoc> I currently go back to the logs, but that list was helpful.
<sarang> I don't want people to have to scour IRC logs
<sarang> Sure, I'll make some issues
<sarang> We should clear out old issues as well, or request updates
<nioc> peanut gallery here. Now that suraeNoether 's matching project is complete (?) or nearly so, what is the plan to use it going forward ?
<atoc> 'scouring IRC logs' - story of my life :')
<sarang> nioc: good question for suraeNoether!
<sarang> He has also been working on LRS security models lately
<sarang> (which are a blocker for CLSAG review)
<sarang> OK, let's move to ACTION ITEMS for the time being (discussion can of course continue after we formally adjourn)
<sarang> I am writing up some material on transaction proofs/assertions, and writing up new code for a proposed InProofV2 and OutProofV2
<sarang> As well as security model updates, some work on proof rewinding for data storage, and some odds and ends
<sarang> Anyone else?
<atoc> my action item: mkW my private .git repo (of atomic swap implemntation) public on Githuv
<koe> my action items: multisig and escrowed-marketplace protocol writeup, possibly start bulletproof study if time permits
<sarang> BPs for the ZtM writeup?
<Isthmus> I want to make a website where you can type in a stealth address (or list of them) and see what future transactions have used them as ring members
<Isthmus> But need a little bit more backend work before that is ready
<koe> at the very least studying it
<Isthmus> I think the concerning part will be seeing the outputs that have been used in no subsequent rings, and thus have a known spend state and no plausible deniable for spendedness
<sarang> Let me know if you have any particular questions that I may be able to answer
<koe> of course :)
<sarang> Any other action items, or final comments before we adjourn?
<sarang> (from anyone)
<koe> actually spoiled my writeup from several months ago in the latest ztm2 draft whoops
<sarang> It's great to see so much research lately into so many different areas of interest from so many people :D
<sarang> Gets tough to keep up with everything
<sarang> Which is a great problem to have, in some sense
<sarang> Anyway, thanks to everyone for attending; we are now adjourned!