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WhatsApp's Signal Protocol integration is now complete

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Re: WhatsApp's Signal Protocol integration is now complete

#291

Post by mobad »

defiancedigital wrote: post #247

I'm looking at libaxolotl-c. I'm a little bit disturbed about perfect forward/future secrecy. Perfect forward secrecy ensure that a session key cannot be compromised if a long-term key is compromised in future. With something like OTR even if a session key is compromised at n, session key at n-1 or n+1 will not be compromised. Here, we got perfect forward/future secrecy. If i take a look at axolotl, in scenario Alice…

Perfect forward secrecy is actually the opposite of what you mentioned.

"In cryptography, forward secrecy is a property of secure communication protocols in which compromise of long-term keys does not compromise past session keys."

https://www.wikiwand.com/en/Forward_secrecy

If someone were to compromise your key and they had a packet log of all your communication then PFS, which Signal has, guarantees that they wouldn't be able to derive previous keys from the current key to decrypt previous messages from the packet log that came before the key compromise.

The thing you're talking about can be resolved by revoking compromised keys but knowing when to revoke those keys is a whole other problem that hasn't been solved by anyone to my knowledge...

Re: WhatsApp's Signal Protocol integration is now complete

#292

Post by ikawe »

defiancedigital wrote: post #247

I'm looking at libaxolotl-c. I'm a little bit disturbed about perfect forward/future secrecy. Perfect forward secrecy ensure that a session key cannot be compromised if a long-term key is compromised in future. With something like OTR even if a session key is compromised at n, session key at n-1 or n+1 will not be compromised. Here, we got perfect forward/future secrecy. If i take a look at axolotl, in scenario Alice…

"Perfect forward secrecy" requires synchronous key exchange. The compromise that signal protocol makes is for forward secrecy to "eventually repair" itself while in the meanwhile a limited number of messages are potentially vulnerable. That is one of the novel feature of the protocol and it is what allows for async communication without some central server doing all the key mgmt (central key mgmt doesn't have this problem because it's actually synchronous).

I am not a cryptographer.

Re: WhatsApp's Signal Protocol integration is now complete

#293

Post by [deleted] »

defiancedigital wrote: post #247

I'm looking at libaxolotl-c. I'm a little bit disturbed about perfect forward/future secrecy. Perfect forward secrecy ensure that a session key cannot be compromised if a long-term key is compromised in future. With something like OTR even if a session key is compromised at n, session key at n-1 or n+1 will not be compromised. Here, we got perfect forward/future secrecy. If i take a look at axolotl, in scenario Alice…

[deleted]

Re: WhatsApp's Signal Protocol integration is now complete

#294

Post by jodrellblank »

avn2109 wrote: post #91
stormbrew wrote: post #53

Earlier quoted context omitted.

It seems like there could be a lowest-common-denominator set of phonemes that such a system could be built on, with translations into symbol groups for different languages. As long as those symbol groups are relatable by two people who speak the same language, that might be sufficient?

>> "lowest-common-denominator set of phonemes" They already spent a bunch of time and effort finding these phonemes to build Esperanto, right?

No, see this criticism of Esperanto phonemes: http://www.xibalba.demon.co.uk/jbr/ranto/#b

Its choices are large, irregular, unclearly defined and basically Eastern Polish.

Re: WhatsApp's Signal Protocol integration is now complete

#295

Post by jamesdwilson »

feld wrote: post #265
jamesdwilson wrote: post #107

Earlier quoted context omitted.

fair enough! https://www.schneier.com/blog/archives/2016/03/possible_gove... i think this is why source is a must. if a user compiled and installed the app themselves, and hypothetically had the entire stack above it be similarly open, then it would prevent the kind of attack mentioned. do you agree? if the source is closed anywhere in the stack, or pushed out in a walled garden as it is currently, then it allows the…

iOS is not completely open source, so how do you know that Apple isn't scraping your screen or the iOS keyboard isn't sending your characters? Also, Apple's push messaging subsystem gets a copy of (most) of the message too so Apple could be doing evil things there too! OH NOES!

i agree! the full stack needs to be opened.

Re: WhatsApp's Signal Protocol integration is now complete

#296

Post by kijiki »

greenspot wrote: post #22

Great news. I'm just wondering why Facebook/Zuck is doing this. Is he fearing the competition–all the other E2E messengers out there? I'm asking because I could imagine that Whatsapp might get banned in some countries soon (as recently happened in Brazil) and thus, lose market share.

I'd imagine Zuck is going along with it because WhatsApp announced that they were going to do this before the acquisition closed.

Zuck is way too savvy to publicly reverse that announcement once the deal closed. Imagine how bad that would look...

Re: WhatsApp's Signal Protocol integration is now complete

#297

Post by Joof »

tveita wrote: post #190
tptacek wrote: post #168

Earlier quoted context omitted.

That's something that's at least somewhat true of OTR and PGP too, in their normal use, and in all three cases if you're serious about OPSEC you can completely mitigate the problem. So in my evaluation, Signal's a tier 1 option, and WhatsApp is tier 2. Reasonable people can disagree, of course. I hope it's obvious that, since OTR is in tier 1, these tiers aren't an analysis of how much I like different messengers. :)

> That's something that's at least somewhat true of OTR and PGP too Well, OTR is just the protocol, implementations vary in how well they make you authenticate your conversation partner. And PGP will whine at you a lot if you haven't marked a key as trusted. But somewhat agreed. A bad UI can ruin the security of otherwise solid crypto. I just don't see how the security of Signal and WhatsApp are different. Assuming f…

Its probably only a half-step up, but signal's client (and server?) are open source. You could compile your own to avoid problems with the binary blob being different. Maybe you could run your own server to dish out keys, but that may be a stretch.

Re: WhatsApp's Signal Protocol integration is now complete

#298

Post by danjoc »

tptacek wrote: post #119
jamesdwilson wrote: post #107

Earlier quoted context omitted.

fair enough! https://www.schneier.com/blog/archives/2016/03/possible_gove... i think this is why source is a must. if a user compiled and installed the app themselves, and hypothetically had the entire stack above it be similarly open, then it would prevent the kind of attack mentioned. do you agree? if the source is closed anywhere in the stack, or pushed out in a walled garden as it is currently, then it allows the…

I understand what you're saying. I don't think source is bad thing! Source is good. But I think you're a little confused here. The cryptographic building blocks of the new WhatsApp protocol are available in source code. You can get source for the Signal Protocol (fka Axolotl). You can get source for the Noise framework. WhatsApp borrowed these tools from a very open secure messaging project. You're unhappy that the s…

>If WhatsApp is so evil that they've backdoored their product, it is ... stupid to leave that backdoor in their source code.

Reproducible builds[1] are the solution to that problem. Everyone doesn't have to build the source if a) building the source produces the exact same binaries every time, and b) source can be built by a trustworthy party to verify that it matches the build being distributed. This way, you only need one good build cop to warn the rest of the population about bad binaries.

Signal for Android supports reproducible builds[2] so it seems entirely possible an open source WhatsApp client could as well.

[1]https://reproducible-builds.org/

[2]https://github.com/WhisperSystems/Signal-Android/wiki/Reprod...

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