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I'm sorry that you get that impression, but I do appreciate your input.

> Cryptographer Matthew Green on Signal's crypto and code quality (it was called RedPhone/TextSecure at the time of this writing)

That's the application that they sold to Twitter, not the one being talked about here. I do not know how different the code bases are.

It is also around that time that the app had a gaping, amateurish hole in that it was simply leaking everything via logcat. And what does the guy do? Instead of addressing the issue like a professional, he goes on a complete tangent rubbishing F-Droid (https://github.com/WhisperSystems/Signal-Android/issues/53) and then making rather poor excuses as to why you should get your application from the Google store and not from anywhere else.

Excuses which by the way, have been evolving over time. I think he eventually admitted that he wants to keep track of how many users are using it (handy to show to your potential buyers).

He also has a history of lying, such as when he used fake WHOIS details to run his "Google anonymiser" thing. And of course, when he was shut down by the registrar, as you do when someone has given you false details, what did he do? He went to the press to whine about the registrar! After he entered a contract in bad faith, something which happens to be a prosecutable offence. That's the sort of person we are talking about here. I hope you will understand if his word does not exactly fill me with confidence.

> https://www.eff.org/node/82654.

That page starts with: "This is version 1.0 of our scorecard; it is out of date, and is preserved here for purely historical reasons."

And continues with: "the results in the scorecard below should not be read as endorsements of individual tools or guarantees of their security"

> Signal has been analyzed, with favorable results, by academic researchers at least twice:

Yes, I am aware of those. And that is not what validation and verification is which, as I said, in the absence of publicly available design documents, is impossible to do independently. The guy is trying to make it look like he's selling a "secure" communication platform, but if you presented that to a defence contractor (which I have some experience with) you would be laughed out of the building. Proper security is not done like this at all. For a start, you actually define your goals, i.e., what you intend to secure, against what threats, etc., etc. If you can show me a paper with that information I would be grateful.

Notably, you may have noticed that those papers, like Green's, are a protocol analysis, not an analysis of the entire solution. In that respect, you're back to the previous situation: the protocol might be ultra-secure, but if you're still leaking your plaintext on a different channel...

> Moxie Marlinspike and [...] probably wouldn't call themselves "cryptographers,"

At the risk of sounding elitist, what is his academic background? (I elided the other person because I do not know who he is).

> but almost anybody in the field would agree that they are experts on applied cryptography.

What do you base that conjecture on?

Terminology. What you call free software I call open source. As you go on to mention, you can see the source but not use it in any meaningful way. In particular:

> but have clarified that it is indeed ok to build your own binary from the source they provide,

Exactly. Your own binary. From their source.

Build your own binary for someone else, and it's "malware", as the guy had the nerve to call F-Droid in that bug report (here: https://github.com/WhisperSystems/Signal-Android/issues/53). That sort of bad faith, coming from a known liar (see my other reply) is what I really cannot condone.

> and use their servers.

Yeah, similarly. Use a source other than theirs or servers other than theirs and they start whingeing.

That is not open source.

> I'm not quite convinced about their argument for official app store distribution and updates,

Possibly because every time it's a different excuse?

> but I can understand the argument.

Yes, so can I: they want to control the platform so that it is their users, so that they can sell it to someone else, like they did last time.

And I would be perfectly fine with that, if it wasn't done via lies, deception, and denigrating third parties, particularly the chaps at F-Droid who at least have the decency of using their real names (not to mention not seeing you as the product).

> Sticking with an app store does require trust in the provider though.

Agreed. How high is Google in your "trusted" list? Yes, I'm picking on Google because it's a bit of an easier target than Apple, but still.

> I think it would be best to avoid FUD.

I agree, and that's precisely why I feel the need to speak up. I challenge the honesty not of their enterprise (which is no different from that of Skype, Whatsapp, or any other player) but of the way they are pursuing their goal. See above.

> It certainly strikes me as one of the better options for pragmatic secure messaging,

I don't know. As mentioned elsewhere, XMPP meets all my requirements and is not vendor-dependent. But the availability of options depends on each user's definition of things like "pragmatic" and "secure" (and even "messaging" for that matter!)

From seeing what's out there though, it appears that modern versions of Whatsapp (which I don't use, I'm FOSS-only) offer essentially the same capabilities as this application though, including end-to-end encryption. And of course, essentially the same disadvantages. I could be mistaken here though.

> that allows for a fairly narrow and reasonable set of threats (Google/Apple/Microsoft (possibly more than one of each, depending on your platform), Whisper Systems themselves, probably most state actors).

I guess it also depends on each user's definition of "fairly narrow and reasonable". :-)

> Signal uses Google Play Services to notify me that I have an incoming message from Signal.

More importantly:

a. That dependency, along with other "restrictions", sets an artificially high barrier to actually using the product independently. This is presumably so that they can maintain the pretence of being "open source".

b. Keep track of application downloads and whatever else Google provides to developers.

Moreover, as the paper that someone has linked elsewhere says, if you are allowing Google services in your app (Google Cloud Messaging, to be exact), you're at the mercy of anyone with control of it. A relatively trivial attack via GCM, as the paper hints, would involve simply replacing your application with a backdoored version, and you'd be none the wiser. It is a massive attack surface that just cannot be ignored.

You need to do a threat analysis.

I did not immediately find any good introductory resources via a quick Google search, but try it yourself. Very very briefly, it involves identifying the threats and their possible consequences, then working on either removing the former or minimising the latter.

Be aware that this is not merely a technological process. It is primarily a social one.