Comment by tptacek | Hacker News Reader

Comment by tptacek | Hacker News Reader

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mpOTR sacrifices forward secrecy and provides transcript consistency with limited semantics, which has the side effect of making the "transcript integrity feature" trivial to implement, because the protocol supports only a silly version of it. mpOTR clients can't simply fix this with UI, because these are properties of the protocol.

The TextSecure protocol retains forward secrecy at the message layer and provides continuous transcript integrity. The TextSecure client hasn't worked out the UI for it, but the protocol supports it. TextSecure can provide continuous transcript integrity with a UI update --- something mpOTR clients can't do at all.

But here you are, sniping at TextSecure for lacking a UI feature that you've implemented a minimal and un-useful version of. Then, when called on it, you retreat to a position of "I'm inspired by TextSecure and am just trying to help". As if, after blogging about why transcript integrity is literally one of the reasons TextSecure doesn't use mpOTR, they were unaware of the importance of the feature.

mpOTR is a dead end. It's unfortunate you invested in it, but that is what it is.

It doesn't matter what kind of transport integrity the underlying protocol has if that integrity information isn't actually used. What's more, it's not just that they haven't got around to implementing UI for it, the problem is they can't figure out how to meaningfully expose that information in the UI - which, with consistency semantics this complicated, is actually the hardest part of the problem! They don't even really have the outline of a solution, let alone the transcript integrity you're claiming they have. Yet here you are treating their vapourware as though it provides more protection than something that actually exists.

The UI for transcript consistency is absolutely not the hardest part of the problem. We are comparing an existing UI on top of a broken transcript consistency feature to a nonexistent UI on a functional, extant transcript consistency protocol. I am objecting to the notion that an extant UI built on a mound of sand somehow trumps a concrete foundation poured for a better UI.

This is apparently so much the case that Nadim has acknowledged jettisoning his existing protocol to come up with a new protocol that will support it.

You could disagree with me, but I don't think you can do so without acknowledging that the comment that introduced this issue to the thread was... let's say "not fully informative".

UI is absolutely a very difficult part of the problem, and here we see an example outlining this. Even a capable protocol still has problems if the UI fails to translate the capabilities into benefits and security increases for users. I speak from experience: Cryptocat has had some serious issues that were due simply to incomplete UI, the most recent of which was related to authentication.

Also, the reason for us moving to a new protocol has more to do with formal security proofs than being able to adopt new properties.

This is a comment that appears to endorse mpOTR's broken transcript consistency feature. Also: formal security proofs? Really?

Some context: http://tobtu.com/decryptocat.php

(Yes, we know you addressed these issues; the page I just linked to says that).

It really seems like you wrote this comment not to add anything to the conversation, but simply to discourage me from commenting. I really don't understand. I'm trying to be constructive here and I wish you'd join me. Your comment right now just flails around for abrasive things to put together into a statement that is completely incoherent and off-topic.

Your inability to respond to my actual comments appears almost willful. Let's break this down:

* You complained about TextSecure's "lack" of transcript integrity.

* I pointed out that transcript integrity was a prominent feature of the blog post we're talking about, and a feature that the actual TextSecure protocol does vastly better than mpOTR.

* Someone else objected to allusions to TextSecure's transcript consistency feature as vaporware, given that Cryptocat actually has a UI for this.

* I pointed out that the protocol Cryptocat builds that UI on is so bad that you conceded downthread that you're building a new protocol --- you made that concession in direct response to my point about mpOTR's inferior transcript consistency.

* Your response is to imply that improved transcript consistency is not a significant reason for abandoning your existing protocol.

* I point out the inconsistency.

* You object that I'm not "adding anything to the conversation".

Thanks for laying out your thought process, it's very helpful.

> I pointed out that the protocol Cryptocat builds that UI on is so bad that you conceded downthread that you're building a new protocol --- you made that concession in direct response to my point about mpOTR's inferior transcript consistency.

This is the problem. You're assuming that my mention of mpCat was a concession made in "direct response" to your point about mpOTR, whereas it's actually brought up as a tangent. The reason we're building a new protocol is to be able to subject it to formal security proofs, as mentioned prior. It doesn't have to do with the existing protocol being "bad" or not or its current integration into the UI.

Regarding my other implied statements, I think it would be better to stick to claims I am explicitly making instead of assuming implications on my part. That being said, I apologize and will try to be more clear in my future comments in order to avoid assumptions.

I'm also not sure why you keep bringing up mpOTR. As I mentioned in my other post that you refer to, we're not using it anywhere nor do we plan to. We're building a modified version which is far less bulky, etc.

Maybe some other reader can tell me whether Nadim is saying that he endorses TextSecure's continuous transcript consistency model and is working on folding it into his new protocol, or whether he thinks the mpOTR model of consistency checking only at the conclusion of sessions is so useful that not providing it is worth dinging TextSecure over, or whether there's some third option I'm excluding. Because I can't even figure out what Nadim is trying to say anymore.

I endorse continuous transcript consistency, but believe that TextSecure currently does not allow its users to benefit from it and that this should be resolved. I think mpOTR is irrelevant to this discussion. I hope that's clear!

Thanks for agreeing to turn the discussion in a more constructive direction, Thomas.

I agree that mpOTR is a dead end. The initial paper by Goldberg et al describes a protocol that is bulky and largely undefined. I should mention that for those reasons, Cryptocat's group chat effort has been relabelled to "mpCat" instead of "mpOTR" — we're moving on to creating a protocol suitable for synchronous use-cases specifically (since TextSecure already has the asynchronous use-case figured out) without shouldering the bulkiness and obsolete nature delineated in mpOTR's original description. One of the things that is actually addressed better is transcript consistency: in mpCat, it will function on a level of reliability that is in fact continuous and not just occurs once per entire conversation.

We recently concluded mpCat's first review summit, and were very lucky to have the feedback of experts such as Trevor Perrin, Joseph Bonneau and Ximin Luo. We also invited members from TextSecure's team in order to help us understand the use-cases scenarios they have experience in. For what it's worth, the TextSecure members that were invited were seen as open source peers, and not as "competitors" as you put it. I should mention that TextSecure's research frequently came up while working on mpCat, and that they are contributing more to this field than most other projects. That's why I say they are inspiring.

Despite the fact that you've fleshed your responses out from single sentences to whole paragraphs, there is still no technical content in this comment that addresses my comment. It appears that your response is "no, we don't properly do transcript consistency either, but we're working on it". But I had to read between the lines of your name-dropping comment to come to that conclusion.

An uninformed reader of your root comment on this thread would be surprised by that concession. Is my conclusion incorrect, or was your original comment deceptive? (Unintentionally, I'm sure.)

My original comment was simply to point out a current problem in this protocol design. There are some ways one can deploy to make it more difficult for Alice to send different messages to Bob and Carol without being detected, and they are deployed in Cryptocat (you're welcome to peruse the codebase and documentation.)

Just as a note, I'm sincerely discouraged from attempting to have an informative discussion with you by the fact that you keep assuming bad faith on my part, and generally responding in a needlessly rude and aggressive fashion. Consider that your general approach in this particular discussion might be why information security has a bad name as a poisonous field. If I don't reply to parts of your post, consider that it is because they are phrased in a way that assumes and implies a complete understanding, wrapped in aggression and the assumption of bad faith. I'm not here for that kind of discussion.

Your original comment is right there for readers to see, as is Moxie's post, which covers the issue in depth.

People can decide for themselves whether you meant to "point out a current problem in the protocol design" (a confusing question, given that your objection is about UI). You know what I think already.

gj implying on twitter that your followers should upvote your comments lol https://i.imgur.com/FI6IdaO.png

That is incredibly annoying, because it will probably have the effect of setting off the ring detector and burying the story, which is too bad, because the TextSecure post we're talking about here is excellent. I'll let the mods know. Thanks for catching this.

Looks like he has two accounts too...

jesus christ fuck already

No thank you.

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