Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Telegram’s Cryptanalysis Contest

cryptofails.com

Post reply on HN
Print view View original

11–20 of 138 posts

Re: Telegram’s Cryptanalysis Contest

#11

Post by Beltiras »

StavrosK wrote: post #9
simias wrote: post #6

Earlier quoted context omitted.

In particular none of the attacks described in TFA (Known Plaintext, Chosen Plaintext and Chosen Ciphertext) are possible within the frame of their contest (since Telegram controls all inputs). Yesterday someone blogged an example of a completely broken cryptosystem that would still pass Telegram's challenge with the same limitations: http://www.thoughtcrime.org/blog/telegram-crypto-challenge/

That's Moxie Marlinspike, developer of TextSecure.

With a very valid challenge.

Re: Telegram’s Cryptanalysis Contest

#13

Post by Confusion »

raverbashing wrote: post #8

Funny how they say "oh but the attack possibilities are limited" then proceed to mention all the weaknesses in the algorithm. Well, if the algorithm is so broken then it should be trivial to break it even with their limitations. Isn't that what they say? "Oh SHA-1 is broken", great, show it. Of course, the capability to do that may be worth more than getting the $200k from the contest

  Well, if the algorithm is so broken then it should be 
  trivial to break it even with their limitations.
Well, if the house is so badly protected, it should be trivial to break in, even with their limitations[1].

[1] Limitations include: not being allowed within 200m of the house.

Re: Telegram’s Cryptanalysis Contest

#14

Post by Confusion »

kayoone wrote: post #12

Some strong claims in there for not really proving that the protocol is indeed "terrible".

An expert on trees:

  This oak is probably diseased. It has discolorations on 
  some of the leaves and the bark is much looser than 
  normal. I think it should be thoroughly investigated or 
  perhaps just cut it down to be safe.
kayoone, knowing nothing of trees: "some strong claims in there for not really proving that the tree is indeed diseased."

Re: Telegram’s Cryptanalysis Contest

#15

Post by raverbashing »

simias wrote: post #6
testing12341234 wrote: post #5

Earlier quoted context omitted.

The easiest to understand response to this question that I've seen so far is from this comment [0]: The contest limitations rule out most of the likely attack vectors for breaking the protocol in the real world. It's like saying "Our bank vans are 100% secure. Just try stealing money from them without puncturing our tires or bribing one of our employees." [0] - https://news.ycombinator.com/item?id=6936949

In particular none of the attacks described in TFA (Known Plaintext, Chosen Plaintext and Chosen Ciphertext) are possible within the frame of their contest (since Telegram controls all inputs). Yesterday someone blogged an example of a completely broken cryptosystem that would still pass Telegram's challenge with the same limitations: http://www.thoughtcrime.org/blog/telegram-crypto-challenge/

It may even be possible to factor the RSA Key

More to the point, KPA,CPA, etc are very important, and systems should be definitely tested against them, but in real attacks, they may not be available

Re: Telegram’s Cryptanalysis Contest

#17

Post by zAy0LfpBZLC8mAC »

raverbashing wrote: post #8

Funny how they say "oh but the attack possibilities are limited" then proceed to mention all the weaknesses in the algorithm. Well, if the algorithm is so broken then it should be trivial to break it even with their limitations. Isn't that what they say? "Oh SHA-1 is broken", great, show it. Of course, the capability to do that may be worth more than getting the $200k from the contest

Yeah, it's like saying "oh but the attack possibilities are so limited" to then proceed to mention how all the components can't bear the load of the bridge.

Well, if that piece of steel can so obviously not hold those 10000 tons of concrete given the corrosion over the next 30 years, it should be trivial to break it even with their limitations.

It has been shown that SHA1 is broken - it's just that experts in the field tend to be able to know such things before the bridge has collapsed, but that does not mean that they can demonstrate it to anyone who doesn't want to study the theories behind their assessment without building the bridge and waiting 30 years.

Re: Telegram’s Cryptanalysis Contest

#18

Post by raverbashing »

Confusion wrote: post #13
raverbashing wrote: post #8

Funny how they say "oh but the attack possibilities are limited" then proceed to mention all the weaknesses in the algorithm. Well, if the algorithm is so broken then it should be trivial to break it even with their limitations. Isn't that what they say? "Oh SHA-1 is broken", great, show it. Of course, the capability to do that may be worth more than getting the $200k from the contest

Well, if the algorithm is so broken then it should be trivial to break it even with their limitations. Well, if the house is so badly protected, it should be trivial to break in, even with their limitations[1]. [1] Limitations include: not being allowed within 200m of the house.

I disagree

You are allowed access to the encrypted data.

In a real attack you may, depending on the circumstances, only have access to that (at first, at least).

Probably more like "you aren't allowed to destroy any locks or doors to enter the house". Hard, but much different than staying 200m from the house.

Re: Telegram’s Cryptanalysis Contest

#19

Post by raverbashing »

zAy0LfpBZLC8mAC wrote: post #17
raverbashing wrote: post #8

Funny how they say "oh but the attack possibilities are limited" then proceed to mention all the weaknesses in the algorithm. Well, if the algorithm is so broken then it should be trivial to break it even with their limitations. Isn't that what they say? "Oh SHA-1 is broken", great, show it. Of course, the capability to do that may be worth more than getting the $200k from the contest

Yeah, it's like saying "oh but the attack possibilities are so limited" to then proceed to mention how all the components can't bear the load of the bridge. Well, if that piece of steel can so obviously not hold those 10000 tons of concrete given the corrosion over the next 30 years, it should be trivial to break it even with their limitations. It has been shown that SHA1 is broken - it's just that experts in the fie…

It looks to me the SHA1 part is the least of their worries.

Yes, the pillar may corrode in 30 years, but the load is actually on a smaller and frailer pillar

Post reply on HN