Challenge "Weakened ElsieFour — Part 3"  

  By: admin on Oct. 3, 2017, 6:39 a.m.

The challenges for the weakened ElsieFour serve as an exercise and use an intentionally weakened version of LC4. ElsieFour combines ideas of modern RC4 stream cipher, historical Playfair cipher and plaintext-dependent keystreams. It can be computed manually. Part 3 is a partly-known-plaintext challenge which provides 2 messages that were encrypted with the same key.

 Last edited by: admin on Oct. 31, 2021, 2:55 a.m., edited 3 times in total.

Re: Challenge  

  By: nicosPavlov on Jan. 31, 2018, 5:56 p.m.


The challenge was interesting, thanks for preparing it.

However, for a "part 1" challenge, it seemed pretty hard. It took quite some processing
to crack it, and I consider myself lucky to have found the solution this fast.
An easier challenge may be a good introduction to the LC4 cipher, perhaps with a partly known key, such as in the Oryx challenge series, which has a quite progressive difficulty in its different challenges.

The new “Advent4” challenge is a nice introduction to LC4, but is simple enough to not really be comparable in terms of how to attack the cipher.

Re: Challenge  

  By: AnLeRo on Feb. 4, 2018, 7:10 p.m.

Thank you for your feedback :)
I am going to prepare another "Weakened ElsieFour" challenge as you suggested as soon as I have enough time.
Best wishes, Anna

Re: Challenge  

  By: AnLeRo on June 3, 2018, 10:44 p.m.

This challenge was renamed from Part 1 to Part 3, because it seemed to be too hard as a part 1.

I hope you enjoy the new Weakened ElsieFour challenges!

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