Hard Live

Defying Hell

100 points

49 Solves

Cryptography

Hard

Noxtal

Community Rating: 4.62 / 5

Alice has been sharing secret encrypted messages with Bob. I would really like to know what those are...

I contacted my good friend Eve, a well-known eavesdropper. She sent me the numbers she found at the beginning of their conversation. By the look of things, this looks like a key exchange. If we would find the key, we would be able to decode every message they encrypted with it!

Help me find both private keys. To submit the flag, decode them correctly and wrap them into CTFlearn{<Alice>_<Bob>} format.

Hint: the title of this challenge is a pun... I can't tell you more ;)

First 10 Solvers

Rank Username
1 ebouteillon
2 Caillou
3 shikame
4 tenchijin
5 0utWrest
Rank Username
6 SketchyDuck
7 mildsunrise
8 voyante
9 usuki123
10 Zonda

  • ebouteillon

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    • Caillou

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      • Noxtal

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      • 0utWrest

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        • Noxtal

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          • Noxtal

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      • 0utWrest

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        • Noxtal

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    • Noxtal

      Absolutely! This challenge has not been designed for that. It is mostly about research: you need to search quite a bit to find good algorithms to solve this challenge. I suggest you check out the Wikipedia page of this key exchange algorithm. :)

      • SketchyDuck

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          • Noxtal

            Glad to hear that, thanks a lot!

  • mildsunrise

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  • voyante

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    • voyante

      ok :) solved forgot that there can be last step!

      • Noxtal

        Glad to hear that, congrats! Thanks for trying my challenge! :)

  • Veritas

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    • Noxtal

      Try converting the keys to something human-readable ;) Hope it helps :)

  • Lriend

    Thanks for this challenge. Amazing one <3

    • Noxtal

      Glad to hear that! Thanks!! <3

  • Celebrity

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  • Celebrity

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    • Noxtal

      This is a way of doing it, but I don't think it's the more efficient one since you'll probably need to try more than 500k values (I haven't tested it though). To help you further with that method, I would like to know which language this snippet is, please. To me, it looks like Python, and if it indeed is, then your one-liner has an invalid syntax... Btw, sorry for the late answer, I was taking a break of computers. :)

      • Celebrity

        it is python , what is the most effiecent way just give me hint , I would like to learn that

        • Noxtal

          Your oneliner seems invalid to me, you might want to fix that... For the most efficient way to do it, it's not bruteforce, that I can tell you for sure. If you know what technique this challenge is about, then the Wikipedia page for it contains a section you might want to check. ;) That's all I can tell you without spoiling the challenge. If you still have difficulties, hmu on Twitter @noxtal_, I'll be glad to help :)

    • Noxtal

      Thanks man! Glad to see you've liked it! :)

  • mhase

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    • Noxtal

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