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Keybase Exploding Messages

keybase.io

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Re: Keybase Exploding Messages

#21

Post by e1ven »

ohazi wrote: post #9
e1ven wrote: post #4

As I understand, Keybase chat is open-source? ( https://github.com/keybase/client ) I don't have time to read through the code right now, but I'd love to hear how they implemented exploding messages with untrustworthy clients. I've thought about it a few times before, and it seems one of the few places that closed software has an advantage - You can't easily force third-party clients to delete messages. If they've so…

It is impossible to implement this feature "safely" even with trusted clients -- worst case I take a screenshot or even a photograph of the device displaying the message before it explodes. If you don't trust the person at the other end, this is never going to work. It's more useful for "we both agree that we don't want a paper trail" kind of thing.

Absolutely - That's my understanding as well.

There are ways to mitigate (snapchat detects screenshots, etc) but no way to fully prevent - Someone could always use an external camera, etc.

I was just really hoping that they had come up with some sort of cool technical way to stop the ability to decode messages after XYZ time, even if they couldn't prevent it from being copied once decoded.

For example, imagine if a message were wrapped in two levels of encryption - Once from the user, and once with a key that you have to retrieve from keybase.io - If you weren't in the right time-window, you wouldn't be able to retrieve the second key.

There's lots of problems with that particular approach, which is why I was hoping they had come up with something awesome, not just asking the client nicely to delete it. It's a nice feature either way, though.

Re: Keybase Exploding Messages

#22

Post by cascom »

arkadiyt wrote: post #7
cascom wrote: post #2

anyone care to expand on the practical applications/implications/threat model where this makes sense?

It's for when you trust someone but don't want to risk either your or their device being compromised in the future. For instance: - if your or their phone gets taken at a border crossing - if your or their phone gets taken by the FBI (which is how they recovered encrypted WhatsApp/Signal chats from Michael Cohen's phone) - etc

thank you - this is what i was looking for

Re: Keybase Exploding Messages

#23

Post by schoen »

ohazi wrote: post #19
SamuelAdams wrote: post #18

Consider this: I send an exploding message, set for 1 day, to Bob. Bob checks his chat a week from now. Does Bob get the message? Or has it already exploded? I guess I'm asking when the actual explosion timer starts - when the message is sent, or when it is read? For group messages, do all parties need to read it before the timer starts?

From the FAQ: Does the timer begin when the message is sent or received? Sent. This seems like the only sensible answer for group chats. And we can't have a different answer for 1-on-1 chats and group chats. That would confuse people. Not the kind of person who reads an FAQ such as yourself, of course. So our answer is simple: you set a timer and the message is gone after that time.

I believe Signal uses the other policy, that the timer starts when the message is read rather than when it's sent.

Re: Keybase Exploding Messages

#25

Post by tylersmith »

Sir_Cmpwn wrote: post #8

This very article shows you the problem with "features" like this. You see that video demonstrating the feature? Notice how you can read the content of the message which was supposedly deleted?

In theory not having the signatures means the messages could be falsified, but many people would trust a screen capture still. Regardless, the signatures themselves could be extracted before "exploding" so the feature really is promoting unsafe security assumptions

Re: Keybase Exploding Messages

#26

Post by tedunangst »

ggg9990 wrote: post #20
ohazi wrote: post #9

Earlier quoted context omitted.

It is impossible to implement this feature "safely" even with trusted clients -- worst case I take a screenshot or even a photograph of the device displaying the message before it explodes. If you don't trust the person at the other end, this is never going to work. It's more useful for "we both agree that we don't want a paper trail" kind of thing.

A dead simple way to thwart the “screenshot” attack is to release a tool for accurately falsifying a screenshot. I’ve never seen this employed in practice though.

How is any bitmap editor not such a tool?

Re: Keybase Exploding Messages

#27

Post by WorldMaker »

tylersmith wrote: post #11
schuetze wrote: post #6

Earlier quoted context omitted.

It works as long as no one takes a screenshot.

Or even extract the text + signature before it "explodes". Keybase messages don't have repudiability so anybody who has received a sign message should be considered to always have that message.

Though the FAQ at the bottom of the article suggests some sort of minimal repudiation support is in the works.

Re: Keybase Exploding Messages

#28

Post by tylersmith »

Kenji wrote: post #13

Exploding messages are a stupid gimmick that does not hold up to any nontrivial threat model. What's out there is out there. Clients programmed to throw away plain- and ciphertext can simply be modified to keep them. Is the intersection of the set of clueless fools and set of people who want to use strong encrypted chats really this large??

Your languages is stronger than I'd use, but this feature really is irresponsibly promoted at best and maybe just flat out irresponsible altogether for a "security" product.

Re: Keybase Exploding Messages

#30

Post by pphysch »

Kenji wrote: post #13

Exploding messages are a stupid gimmick that does not hold up to any nontrivial threat model. What's out there is out there. Clients programmed to throw away plain- and ciphertext can simply be modified to keep them. Is the intersection of the set of clueless fools and set of people who want to use strong encrypted chats really this large??

I think this is precisely the target demographic--rather than cluelessly keeping a log of sensitive messages, the end user can cluelessly "explode" their sensitive messages. Of course, the clueless user will probably forget to do this anyways and it should probably be a default feature for the clueless organization.
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