March 11, 2019
<sarang> Our meeting begins presently
<sarang> Let's go ahead and get started. Agenda is here: https://github.com/monero-project/meta/issues/314
<suraeNoether> howdy everyone
<sarang> 1. GREETINGS
<MRL-discord> <Isthmus> Hello! Biking, in soon.
<sarang> Let's recap 2. NETWORK UPGRADE
<sarang> Kudos to everyone for a successful first upgrade
<sarang> I don't recall when the second was slated to occur, since block arrival was stunted
<sarang> Any thoughts on the upgrade after the fact?
<xmrmatterbridge> <rehrar> Hi
<sarang> I believe it was dEBRUYNE who wanted an upcoming meeting specifically to talk more deeply about the future of PoW
<parasew[m]> anyone monitored the "old chain"? if there have been this large amount of asics on there, and not turned off it should be visible
<sarang> I believe sgp_ ran some blackball numbers on it
<sarang> and found essentially nothing of interest
<sarang> but as far as hashrate, I am not sure
<sgp_> yeah, no chain reactions so far, very few known spent outputs through reused key images
<sgp_> impact on network privacy so far is essentially 0
<sarang> sgp_: were the key image reuse numbers for only v9 and v10?
<sgp_> yes, just those two
<sarang> great, thanks
<sarang> Relating to this, we can also introduce 3. NEXT POINT RELEASE
<sarang> Not all desired non-consensus changes made it in to this release, so Sometime Soon (tm) will be a point release
<sarang> BP optimizations will be one nice addition
<sarang> I would like output selection to also be included… we talked about it at length at an earlier meeting
<dEBRUYNE> sarang: Correct. It's a topic with a lot of depth that requires an extensive discussion imo
<sarang> suraeNoether: do you have a current recommendation for output selection?
<suraeNoether> i'm running into problems testing the matching code, based on this problem too
<sarang> Here is a discussion of the different algorithms: https://github.com/monero-project/meta/issues/307#issuecomment-466514757
<suraeNoether> iirc the output lineup method performs quite well
<sarang> I prefer it among the others that were tested
<sarang> But it's a change that deserves more than two thumbs-up :)
<suraeNoether> there is no optimal solution, but some solutions are better than others and the output lineup method is more reasonable than the other proposals, and i have no new proposals to make (yet)
<sarang> I updated the sim code (link in agenda) to examine the output weighting in more details
<sarang> Hopefully the BP optimizations are less contenious
<suraeNoether> uhm i think i have one possible proposal that i want to chat about with you by side channel to hash out some details
<sarang> We should have a formal recommendation before whatever date is set for the point release code freeze
<sarang> Anything else relating to the point upgrade that ought to be discussed?
<sarang> ping moneromooo perhaps
<xmrmatterbridge> <rehrar> I just want timelines. Nothing to say on content.
<moneromooo> What's the question ? :)
<moneromooo> I don't know about any date. Depends when we get all the stuff on master ready really.
<sarang> Anything relating to the next point release you'd like us to discuss?
<moneromooo> None that come to mind right now.
<sarang> In that case, let's move to 4. ROUNDTABLE
<sarang> suraeNoether: care to go first?
<sarang> OK, I can go first instead
<sarang> aha, go ehead
<suraeNoether> Well, my simulations for the matching code are to the point where i'm running a matching on some test data now to generate a confusion matrix.
<suraeNoether> i'm also editing the manuscript describing the whole process
<suraeNoether> one of the problems i'm running into is actually simulating our output selection in part because it's not clear which direction we are going yet
<suraeNoether> and it occurred to me that this could help inform our choice of output selection by seeing if one of these possibilities makes matching easier or harder
<sarang> IMO matching expect spend with proper weighting seems optimal enough from a purely timing perspective
<sarang> (leaving out questions of binning etc)
<suraeNoether> when i say easy or hard i don't mean in terms of time, because as we've seen matching is essentially super duper fast
<suraeNoether> i mean in terms of false negative and false positive rates
<suraeNoether> but you are 100% on that
<sarang> aw shucks
<suraeNoether> i'm working on a variety of other side things but i'm shooting for this matching paper to be complete and published some time in the next 2 months
<suraeNoether> if we get more speakers for the konferenco, then i won't be speaking, but otherwise i will probably be presenting on this at the konferenco
<sarang> Neat; anything else of interest to share?
<suraeNoether> that's all i have today, thanks!
<sarang> I have a few things
<xmrmatterbridge> <learninandlurkin> The line up is looking great btw! Fantastic effort for a first konferenco
<suraeNoether> catching up on lots of reaidng in algebraic geometry :D
<sarang> First, my next FFS/CCS will be posted soon
<sarang> As was discussed here, in -community, and elsewhere, the request will be for immediate payout
<sarang> This means both donors and I know the actual value of the donations
<sarang> Since this is a big change, any questions or comments on it?
<sarang> (presumably suraeNoether will be doing the same arrangement)
<suraeNoether> i'm in support of this, and i will indeed be mimicking this
<sarang> Folks who do not trust us to run with the money should, of course, not donate
<sarang> But my hope is that our records have shown we're good for it :D
<binaryFate> happy we came to that solution eventually, hopefully will be better for your guys
<sarang> Thanks to binaryFate and others for agreeing to this change
<binaryFate> yes the idea is that donors being careful should discourage randomers to do the same
<sarang> The CCS posting will _very_ clearly state the arrangement, so there is no confusion
<binaryFate> If you figure out the markdown
<sarang> Yes indeed
<moneromooo> Technically, it's within the existing rules as stated: one milestone, which consists of "sarang starts working" :)
<sarang> Second, the paper that suraeNoether and I have been collaborating with external researchers on (DLSAG et al.) is in final review now
<sarang> We've been asked not to share it before it's released as a preprint, as a courtesy to all authors
<sarang> It has some great details on useful constructions that I'm sure we'll discuss at length after the preprint goes to IACR
<sarang> it'll be submitted for a conference as well
<sarang> Third, I wrote up some additional tests and code for Bulletproofs MPC
<dEBRUYNE> sarang: How does this work if the proposal is not fully funded yet when your period starts?
<sarang> Two options: either the bulk is paid out and it stays open until filled
<sarang> or it all sits there until fully funded
<sarang> I prefer the first, but am open to discussion
<sarang> Regarding Bulletproofs MPC, real_or_random had some great thoughts on this before the meeting (but I won't put him on the spot)
<suraeNoether> i imagine that the important part is laying out which way it goes in the proposal
<sarang> the question has to do with what a malicious player can do
<sarang> We chatted about the fact that an evil player could try to pull what amounts to a cancellation of partial proof elements, effectively setting the inputs to the hash that generates a F-S challenge
<sarang> I couldn't find a way that this could be used as an exploit, aside from obviously generated an invalid proof
<sarang> but the security proofs for BPs do require that F-S challenges are uniform
<sarang> I had neglected that point when I had thought about this earlier
<sarang> My strong suspicion is that proof elements are still uniformly distributed in the presence of a dishonest challenge due to the prover's randomness, and that you still get zk in this case (but not provably)
<sarang> Moral: if we do anything in the future that requires/desires this scheme, these things would need to be considered
<sarang> Any questions/comments relating to this?
<suraeNoether> i think we should continue to ponder it and write something up formally about the BP MPC schemes
<sarang> Well that's the thing… there's really nothing to write formally
<sarang> You can probably solve all the theoretical woes by having all players commit to their proof elements before multicasting them
<sarang> then an honest prover is guaranteed uniform F-S challenges
<xmrmatterbridge> <learninandlurkin> Sorry but I'm a little out of the loop here. What exactly are BP MPC for? something to do with multisig with BP?
<suraeNoether> it's nice to think about collectively computing BP range proofs, but I'm still v curious about the coinjoin approach that we are considering on the larger scale.
<sarang> Ideally, untrusted parties could generate single BPs for outputs
<suraeNoether> after all, it's hard to even think about threat models unless we know how these things will be used in practice
<sarang> Sure, this is all pie-in-the-sky right now
<suraeNoether> learninandlurkin: collaborating with friends to compute a range proof for a coinjoin style transaction, so that the participants don't reveal their amounts to each other
<sarang> But yes, the threat model would be very different depending on how the rounds go
<sarang> Finally, suraeNoether had shown me this a while back: https://lelantus.io/lelantus.pdf
<suraeNoether> agreed on the commit-and-reveal; expensive but usually does the trick to ensure participants can't be rewound inappropriately
<sarang> An interesting application of some of the fundamentals behind Bulletproofs and the old StringCT scheme
<xmrmatterbridge> <learninandlurkin> So… allowing multi-input transactions where each user doesn't know the amounts of the other inputs? Sounds useful
<suraeNoether> learninandlurkin hence our interest in nailing down threat models *nod*
<sarang> I've been playing around with some of the math in that paper to see what nuggets could be extracted
<suraeNoether> oh i had a brief thing to point out: isthmus and n3ptune at noncesense-research-lab answered one of my requests and we now have a complete empirical distribution of number of inputs and outputs per transaction
<suraeNoether> forgot to mention this:
<sarang> Neato, where is this distribution to be found?
<suraeNoether> the data surprised me
<dEBRUYNE> <sarang> I prefer the first, but am open to discussion <= I'd be OK with the first, but perhaps it would be most convenient to use a rounded number
<dEBRUYNE> e.g. if 211 XMR is funded, pay out 200
<sarang> You won't believe what's in tx_distribution_in.csv!
<dEBRUYNE> Mebbe malware
<suraeNoether> super heavy tails for one thing, and a rootkit for another
<sarang> dEBRUYNE: perhaps a full payout at date X, and then a second payout at either date Y or completion, whichever comes first
<binaryFate> <sarang> I prefer the first, but am open to discussion <– donors will have no incentive to fund in time, it will drag till the end of the period
<sarang> binaryFate: how would you do it?
<binaryFate> I like the incentive to donors of you proposing something and getting to work on it only if funded
<xmrmatterbridge> <learninandlurkin> I imagine coinjoining going on would really complicate output selection. Or is there some idea where they work off each other to get rid of heuristics?
<sarang> Depends on how timely it is
<suraeNoether> learningandlurkin coinjoin brings a whole new nightmare to the party. does everyone bring their own mix-ins? certainly nothing is to stop a malicious party from coinjoining with a bunch of badly selected mix-ins
<moneromooo> A ring is one person only. Fake output selection is untouched.
<sarang> Well each input signs with its own ring
<moneromooo> That person makes their own ring, yes. Otherwise others would know which is the real out.
<sarang> The benefit is breaking the assumption of one-party control of outputs and the link to the input rings
<binaryFate> What about simple attack of using the same 10 decoys as one of the other participants?
<msvb-mob> Is parasew, nevvton, or txmr in the channel?
<binaryFate> mmm you don't know which are decoys, nevermind ^^
<sarang> If this moves forward, hopefully we can determine the necessary practical security for BPs
<sarang> If we can't aggregate, they'd have to be separate for each output
<suraeNoether> my beard is getting very thoroughly stroked this morning. much to think about…
<sarang> I believe we'd get practical security without player commitments, but not provable
<sarang> Anyway: does anyone else wish to share interesting research before we close?
<xmrmatterbridge> <learninandlurkin> Yes it sounds like the interplay between coinjoin and ringsigs will require some diagrams for me to ever understand. Could get complicated.
<suraeNoether> i think you would want a commit-and-reveal stage for everyone to see the ring members to prevent malicious ring intersection in the coinjoin
<sarang> MoneroCoinJoin: an easy 14-round process!
<suraeNoether> isthmus and i have been chatting about methods of extracting the true spend-time distribution from the monero blockchain without knowing exactly which outputs have been spent
<suraeNoether> that's a very nascent conversation, though I think it'll end up being a very straightforward project
<sarang> Discussions in #noncesense-research-lab I presume?
<xmrmatterbridge> <learninandlurkin> so, truish spend-time distribution
<binaryFate> Are there regular meetings on this or just continuous discussion? I had been working on this at some point and have some code around aiming to graphically show the real spend distribution
<sarang> I've seen a few informal conversations in #noncesense-research-lab but didn't know if suraeNoether had something more formal
<suraeNoether> binaryFate: ah, no, this has been a casual conversation by side channel, but there is clearly interest
<suraeNoether> i'll start blabbing about it in here more publicly
<sarang> In the interest of time, let's review 6. ACTION ITEMS and then close to continue discussion afterword
<binaryFate> Ok don't hesitate to ping me on this
<sarang> I will be posting my CCS request soon, tidying up the output selection stuff for a recommendation, getting the DLSAG application paper reviewed and out the door, and playing around with that Lelantus paper when/if I get a chance
<sarang> suraeNoether: ?
<suraeNoether> CCS request, working on simulations and measurable numbers for matching, and looking into using our matching code to answer questions about output selection
<suraeNoether> also casual github maintenance
<sarang> Any final questions or remarks before we adjourn?
<xmrmatterbridge> <learninandlurkin> once you guys have made a recommendation for output selection
<xmrmatterbridge> <learninandlurkin> and it gets implemented, what's the next big focus?
<sarang> There will be much to consider in the realm of refund and payment channels
<xmrmatterbridge> <learninandlurkin> Ooh yes the refund ideas from a while back were really interesting
<sarang> and some aspects of output selection, like linking spends across rings in txns, is not solved yet
<xmrmatterbridge> <learninandlurkin> Seems like a logical next area of research
<sarang> and if coinjoin works out, there will be a lot to consider with that
<sarang> Also transaction relay and network-level anonymity stuff that's still in progress
<sarang> To quote the Simpsons: "like the cleaning of a house… IT NEVER ENDS"
<sarang> But on that note, our meeting does end
<sarang> Thanks to everyone for attending. We're adjourned; let the conversations continue