--- layout: post title: Logs for the MRL Meeting Held on 2019-10-28 tags: [dev diaries, crypto, research] author: asymptotically / Sarang --- # Logs **\<sarang\>** GREETINGS **\<sgp\_\>** hello! **\<sarang\>** I'll give a few moments for others who wish to join **\<sarang\>** OK then **\<sarang\>** Since suraeNoether is unavailable for this meeting due to an appointment, I'll share my recent work **\<sarang\>** I've been working on algorithms and proofs for Triptych, a new transaction protocol **\<sarang\>** The goal is to use a single proof to represent multiple inputs at the same time, including balance proving and linking tags **\<sarang\>** Everything works great with completeness, zero knowledge, and soundness except for one proof component (the linking tags) **\<sarang\>** There's a less efficient version that operates on single inputs, but can be combined for general transactions **\<sarang\>** For this single-input version, modified proofs of security seem to work just fine **\<sarang\>** For this reason, I'll finalize work on the single-input proving system while considering alternate approaches to finalizing the soundness proof for the multi-input version **\<sarang\>** Separately from this, I have a small pull request (PR 6049) for a minor speedup and simplification to the Bulletproofs prover **\<sarang\>** Also separately from this, Derek at OSTIF informs me that an audit group is willing to complete the CLSAG review **\<sarang\>** JP Aumasson has offered to complete a review of the math and proofs for $7200 (USD), and his new company Teserakt has offered to then complete a code review for as little as $4800 **\<sarang\>** He says that including dependencies would increase the time (and therefore the cost), possibly significantly **\<sarang\>** But the timeline could be before the end of this year, if there are no changes required to the algorithms after the math review **\<moneromooo\>** Dependencies, like the src/crypto code ? **\<sarang\>** Presumably. I do not have specific details on what his scope is (but will get this information) **\<sarang\>** One approach might be to review all the changes \_from MLSAG_, to show that CLSAG is no less secure as a whole than MLSAG **\<sarang\>** These changes are fairly minor in the grand scope of the codebase **\<sarang\>** I see there being efficiency advantages to having JP (and colleagues) doing both types of review, but this also reduces the total number of eyes on the combined math+code **\<sarang\>** That being said, JP knows his stuff **\<sarang\>** (he was formerly with Kudelski) **\<moneromooo\>** Adding eyes by having Alice do the math and Bob do the code does not provide anything of value over Alice doing both IMHO. **\<moneromooo\>** Assuming Alice and Bob have similar eyes and brains and proficiency in the relevant fields etc etc etc. **\<sarang\>** So that's my report **\<moneromooo\>** Is any of the new protocols being considered still compatible with multisig ? **\<sarang\>** Aside from CLSAG, you mean? **\<sarang\>** None of them specifically consider it in either algorithms or security model **\<sarang\>** but it's on my list for analysis on RCT3 and (eventually) Triptych, since there are some modifications to RCT3 that I wish to consider (more on this later) **\<moneromooo\>** I mean tryptich, rct3 and... and.......... the other the name of which escapes me. **\<moneromooo\>** lelantus **\<sarang\>** Omniring? **\<moneromooo\>** Also :) **\<sarang\>** Omniring and Lelantus both suffer from some drawbacks at present... Omniring does not support batching, and Lelantus still has a tracing issue unless you remove stealth addressing **\<sarang\>** Looking into batch-compatible Omniring-style constructions with other proving systems is a topic for more investigation down the road that is nontrivial **\<sarang\>** Is there other research that anyone wishes to present, or other questions? **\<moneromooo\>** Also, rather selfishly, would any of them avoid the public-a issue we had for multi user txes ? **\<moneromooo\>** (if known offhand) **\<sarang\>** public-a? **\<moneromooo\>** The problem where users would have to make their a values known to other signers. **\<sarang\>** Ah, that's very unclear to me **\<sarang\>** FWIW: RCT3, Omniring, and Triptych are agnostic to how output keys are generated (though their security models address particular constructions) **\<sarang\>** So my ACTION ITEMS for this week are a bit in flux, mainly because I'll be at World Crypto Conference giving a talk on transaction protocols **\<sarang\>** But aside from that, I want to finish the proof modifications (completeness, SHVZK, special soundness) for the single-input version of Triptych (which can be used in a larger protocol to support multi-input transactions), as well as a more efficient linking tag construction that matches what RCT3 and Omniring propose **\<sarang\>** I also want to backport some of the ideas from the latest RCT3 update to their older version to compare efficiency **\<sarang\>** It's unclear if this could easily be proven secure, or what the efficiency gains would be **\<sarang\>** Their update did essentially two things: fix an exploitable flaw due to a particular discrete log relation, and allow for aggregated proofs of multiple inputs **\<sarang\>** Unfortunately, the latter means potentially large padding requirements that would also incur computational cost to the verifier **\<sarang\>** I want to see how easily the exploit fix could be included in the non-aggregated version... which would avoid this potential verification bloat at the cost of proof size **\<sarang\>** I probably won't have time to do so this week, but it's on my list **\<sarang\>** Anything else of note to cover before we formally adjourn? **\<sarang\>** All right! Thanks to everyone for attending **\<sarang\>** Logs will be posted shortly to the GitHub agenda issue