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Three lessons from Threema: Analysis of a secure messenger

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Re: Three lessons from Threema: Analysis of a secure messenger

#41

Post by godelski »

tptacek wrote: post #35
godelski wrote: post #32

Earlier quoted context omitted.

There is always some trust with private communication apps. No way one can get a completely trustless system. Signal tries to build trust by being open source and by publishing the same documents it sends in subpoenas[0] (i.e. transparency in how they respond to government requests). The lack of understanding how the information was obtained is worthy of increased suspicion albeit not abandonment. There is added susp…

The Threema server isn't open source, is it?

I don't think it is, which is disappointing. But even with Signal's open sourced server I think we still need to trust that they are running said server. Unless you know a way to verify it.

Re: Three lessons from Threema: Analysis of a secure messenger

#42

Post by tptacek »

godelski wrote: post #41
tptacek wrote: post #35

Earlier quoted context omitted.

The Threema server isn't open source, is it?

I don't think it is, which is disappointing. But even with Signal's open sourced server I think we still need to trust that they are running said server. Unless you know a way to verify it.

That was true of Threema, too!

Re: Three lessons from Threema: Analysis of a secure messenger

#43

Post by dustyharddrive »

tptacek wrote: post #35
godelski wrote: post #32

Earlier quoted context omitted.

There is always some trust with private communication apps. No way one can get a completely trustless system. Signal tries to build trust by being open source and by publishing the same documents it sends in subpoenas[0] (i.e. transparency in how they respond to government requests). The lack of understanding how the information was obtained is worthy of increased suspicion albeit not abandonment. There is added susp…

The Threema server isn't open source, is it?

You can’t verify the binaries it’s actually running and the protocol shouldn’t rely on a trustworthy server anyway.

IMO the biggest problem with any of these E2EE apps is using them with iOS users. Apple makes it impossible to extract and inspect the packages without jailbreaking, so most projects don’t bother with reproducible iOS builds.

Re: Three lessons from Threema: Analysis of a secure messenger

#44

Post by dustyharddrive »

sundbry wrote: post #12
dewey wrote: post #6

Not directly related to the topic but how is it that Threema is the only popular secure messenger where you have a random ID to give to people to communicate with and not a phone number (Signal) or have your name show up across all your contacts / groups (Telegram)?

It's not, there's also Session https://getsession.org/

Attached to some cryptocurrency BS :(

Re: Three lessons from Threema: Analysis of a secure messenger

#45

Post by tptacek »

dustyharddrive wrote: post #43
tptacek wrote: post #35

Earlier quoted context omitted.

The Threema server isn't open source, is it?

You can’t verify the binaries it’s actually running and the protocol shouldn’t rely on a trustworthy server anyway. IMO the biggest problem with any of these E2EE apps is using them with iOS users. Apple makes it impossible to extract and inspect the packages without jailbreaking, so most projects don’t bother with reproducible iOS builds.

As the paper demonstrates, you did in fact need to trust the Threema server in some respects.

Re: Three lessons from Threema: Analysis of a secure messenger

#46

Post by dustyharddrive »

tptacek wrote: post #45
dustyharddrive wrote: post #43

Earlier quoted context omitted.

You can’t verify the binaries it’s actually running and the protocol shouldn’t rely on a trustworthy server anyway. IMO the biggest problem with any of these E2EE apps is using them with iOS users. Apple makes it impossible to extract and inspect the packages without jailbreaking, so most projects don’t bother with reproducible iOS builds.

As the paper demonstrates, you did in fact need to trust the Threema server in some respects.

Yeah :(

but that’s why I said “shouldn’t” instead of “doesn’t”.

Re: Three lessons from Threema: Analysis of a secure messenger

#47

Post by sys42590 »

tptacek wrote: post #14

The attacks in this paper are much less damaging than the attacks in the Nebuchadnezzar paper were against Matrix. But somehow, Threema comes out looking even worse: * Threema's end-to-end inner protocol, the one used to exchange messages between actual humans, is based on a single X25519 key, used bidirectionally. It has no forward secrecy. Worse, to prevent otherwise-trivial replay attacks made possible by the simp…

The story around Threema feels a tiny bit like Crypto AG repeating: Reputable Swiss company sells homebrew crypto to unsuspecting parties.

Re: Three lessons from Threema: Analysis of a secure messenger

#48

Post by pvg »

sys42590 wrote: post #47
tptacek wrote: post #14

The attacks in this paper are much less damaging than the attacks in the Nebuchadnezzar paper were against Matrix. But somehow, Threema comes out looking even worse: * Threema's end-to-end inner protocol, the one used to exchange messages between actual humans, is based on a single X25519 key, used bidirectionally. It has no forward secrecy. Worse, to prevent otherwise-trivial replay attacks made possible by the simp…

The story around Threema feels a tiny bit like Crypto AG repeating: Reputable Swiss company sells homebrew crypto to unsuspecting parties.

Crypto AG was effectively owned and operated by intelligence services. There's no evidence at all this is the case for Threema, if anything, you'd expect intelligence services to hide their tracks far better.

'A functional, secure E2EE instant messenger with broad public appeal/usability' is just a very convoluted, readily bungle-able project.

Re: Three lessons from Threema: Analysis of a secure messenger

#49

Post by collaborative »

rainsford wrote: post #27
upofadown wrote: post #4

Threema has responded: https://threema.ch/en/blog/posts/news-alleged-weaknesses-sta... New Paper on Old Threema Protocol

The baffling part of that response is that they could easily have conveyed the same basic message in a much less defensive way instead of making me glad I don't rely on Threema for my messaging security. "Good research, and here's how we've addressed those issues and proactively enhanced our security even further" is a decent story to be able to tell about how you're constantly trying to make your customers safer. Be…

I can empathize with how stressful these reviews can be though

Re: Three lessons from Threema: Analysis of a secure messenger

#50

Post by [deleted] »

sys42590 wrote: post #47
tptacek wrote: post #14

The attacks in this paper are much less damaging than the attacks in the Nebuchadnezzar paper were against Matrix. But somehow, Threema comes out looking even worse: * Threema's end-to-end inner protocol, the one used to exchange messages between actual humans, is based on a single X25519 key, used bidirectionally. It has no forward secrecy. Worse, to prevent otherwise-trivial replay attacks made possible by the simp…

The story around Threema feels a tiny bit like Crypto AG repeating: Reputable Swiss company sells homebrew crypto to unsuspecting parties.

[deleted]
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