4 ms·
If they allow man in the middle attacks then the system is completely and demonstrably broken. The out of band public key verification uses deterministic images
by nwh 13y ago
If they allow man in the middle attacks then the system is completely and demonstrably broken. The out of band public key verification uses deterministic images to confirm that the keys are the same, which can be easy forged given the relatively bad comparison engines in use (humans describing what a pixelated 16px image looks like). At no point is the real key shown to the user, so it's impossible to verify that they're identical through a description.
http://telegram.org/img/key_image.jpg http://telegram.org/img/key_image.jpg
I wager that if they did allow a tampering eavesdropper in their bounty contest, it would be in the same conversation that has already done a key exchange and verification, making it yet more snake oil. You can hardly call something secure when you don't allow real-world MITM attacks in testing.
- utnick 13y agoHow is the key image impossible to describe? There are only 4 possible colors per cell. You just describe it like 0,1,2,3,2,0, etc Just as if you were reading off the real key.
- nwh 13y agoFrom just asking around, most people described the key image to me in terms of the darkest portions and ignored the parts that were lighter. It's easier for the example image to say that there's a dark L and lighter X shape in the center and then assume that the rest is the same. At least, that's how people did when I presented it to them as a challenge.
- velis_vel 13y ago> There's also not that many possible images anyway, there's 8 rows with 8 columns, and 4 possible colours for each pixel. Even not assuming any fuzzy matching (human comparison) it's still very possible to generate keys with colliding image hashes. Uh, 4^(8*8)=2^128 is a pretty large number.
- nwh 13y agoSo it is, I've removed that. I need to sleep more.