If I understood correctly, the Signal protocol generates a new key after every message sent and forgets the previous one. Telegram, on the other hand, renews the key only after 100 messages or one week. Thus, is there a certain attack window (1 week / 100 messages) with Telegram's protocol?


1 Answer 1


I think renew keys after a key generation is problematic because assume that key is already generated by the application. If somehow generate key pass through a function $H(x) = B(preImg(x))$. In simple language a function that somehow analysis key pattern and calculate $n$ pre-images of $x$.

  • $\begingroup$ How does one gets the preimage on SHA-256 $\endgroup$
    – kelalaka
    Dec 8, 2021 at 17:47
  • $\begingroup$ crypto.stackexchange.com/questions/8786/… $\endgroup$
    – Ali Hassan
    Dec 9, 2021 at 5:28
  • 1
    $\begingroup$ I know that but how this really occurs in your answer. I want to see a robust answer, not something like I think... $\endgroup$
    – kelalaka
    Dec 9, 2021 at 8:23

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