Forum

Challenge "Not-so-Secret Message from Malawi — Part II (ECC)"  

  By: admin on May 15, 2010, 1:08 p.m.

It is also important to choose the parameters of an elliptic curve cryptosystem wisely. This was not done in this example, which should enable you to decrypt another ciphertext message from Malawi. The plaintext reveals the codeword, although this time it is not as closely related to the photo.
Read more...

 Last edited by: admin on Oct. 31, 2021, 2:54 a.m., edited 1 time in total.

Re: Challenge "Not-so-Secret Message from Malawi – Part II"  

  By: fretty on July 27, 2011, 4:31 p.m.

Something is really messed up with this "elliptic curve". I have no idea how I am supposed to use this to my advantage.

Re: Challenge "Not-so-Secret Message from Malawi – Part II"  

  By: fretty on July 28, 2011, 12:58 p.m.

Yes, yes…YESSSSSSSS. I've done it!

Re: Challenge "Not-so-Secret Message from Malawi – Part II"  

  By: fretty on July 28, 2011, 2:54 p.m.

Ok, I guess I had a problem with this because I knew too much theory (I am a number theorist with a very tiny knowledge of programming, hence why I find it very difficult to solve most of the level 2 problems).

The curve given is NOT an elliptic curve modulo the prime that is given (we have bad reduction). This is the weakness.

Fortunately the non-singular part of this curve mod p DOES have a group law attatched to it and this group law is much simpler to work with. The discrete logarithm problem is simple to solve on this curve (although I had to search for mathematical patterns).

I did this without having to program a single thing!

Re: Challenge "Not-so-Secret Message from Malawi – Part II"  

  By: fretty on July 28, 2011, 9:49 p.m.

I actually have a second solution to this too, one that makes this even easier to solve but is harder to come up with and requires specialist mathematics.

Re: Challenge  

  By: Integral on Jan. 8, 2014, 7:47 p.m.

Hi,

I find that the discriminant is zero (mod p).
So E is singular.
I also find that c4 = 0 (mod p), so the curve has a cusp…

After I'll have to find the map of the isomorphism between E and the underlying (additive, as I have c4=0) group of Fp.

am I on the right way ?

Many thanks for your advice.

Re: Challenge  

  By: Integral on Jan. 9, 2014, 5:34 p.m.

forget about my question, it's OK a got it…

Re: Challenge  

  By: fmoraes on Nov. 18, 2014, 2:08 a.m.

Can someone give me a hint or nudge on how to attack/solve this problem?

I tried to find some literature or papers on attacks on the problem but I have not seen anything that helps yet.

I know the curve is singular but not much more than that. Sage Math doesn't even let me construct the curve because of its singularity.

Re: Challenge  

  By: be on Nov. 23, 2014, 10:48 p.m.

Can someone give me a hint or nudge on how to attack/solve this problem?

Please send me an email and what you tried with Sage. I guess I can give you a hint. Best regards, Bernhard

Re: Challenge  

  By: fmoraes on Nov. 26, 2014, 6:01 p.m.

Can someone give me a hint or nudge on how to attack/solve this problem?

Please send me an email and what you tried with Sage. I guess I can give you a hint. Best regards, Bernhard

Thanks for the reply, but I have already solved it. I had found literature but had not understood it, until someone pointed out the obvious.

Re: Challenge "Not-so-Secret Message from Malawi — Part II (ECC)"  

  By: DarkFibre on March 10, 2022, 7:55 p.m.

Is this challenge working? I have decrypted it 2 different ways, got the same result both ways, but now what? Is the answer supposed to be binary or text? I've tried all 161 bits, the bits of just the letters, those bits with spaces, bits without spaces. I also tried text of the 1st word, 2nd, both, capital letters...

If binary, can you tell me how many bits total and are there supposed to be spaces every 8 bits as shown or not? If the answer is text, is it all the words, some of them, capitals, lowercase? It's making wait about 30 minutes per attempt now...

Thanks


Currently 16 guests and 0 members are online.
Powered by the CrypTool project
Contact | Privacy | Imprint
© 2009-2024 MysteryTwister team