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Challenge "Sigaba Part 1"  

  By: admin on Oct. 11, 2010, 3:52 p.m.

The encryption with the Sigaba machine was the American counterpart to the German Enigma. But due to the much larger key space of the Sigaba, even today, it is only feasible to break the code if parts of the key are known. This is what this challenge is about.
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 Last edited by: admin on Oct. 31, 2021, 2:54 a.m., edited 1 time in total.

Re: Challenge "Sigaba Part 1"  

  By: rwst on Oct. 26, 2010, 7:51 p.m.

Hello,
I'm of the opinion that the author, if he intended to make this a Level II challenge, failed in this intention because he overlooked the fact that if the plaintext appears NOT at the beginning of the message then (after 10-15 characters) the full cipher block configuration must be searched—the given initialisation "ABCDE" will be scrambled to randomness and no longer helps. This means the workload multiplies with 26^5 and my C program that looks only for the cipher block config will need 12 years.

If I'm right I would suggest giving the start six characters of the message instead of a piece in the middle.

Regards,
ralf

Re: Challenge "Sigaba Part 1"  

  By: Schoetti on Oct. 27, 2010, 12:09 p.m.

Hi Ralf,

maybe the wording in the challenge text is a little bit confusing but the given plaintext appears AT THE BEGINNING of the searched plaintext. Otherwise why should the file be called wwiiINITplain.txt???
And so it is feasible to resolve this challenge and it is definetly a Level 2 challenge…

Good Luck!
Pascal

Re: Challenge "Sigaba Part 1"  

  By: rwst on Oct. 27, 2010, 5:42 p.m.

maybe the wording in the challenge text is a little bit confusing but the given plaintext appears AT THE BEGINNING of the searched plaintext. Otherwise why should the file be called wwiiINITplain.txt???
And so it is feasible to resolve this challenge and it is definetly a Level 2 challenge…

Thanks for clarification. It still leaves me with 10^9 general configurations to test but that's better than anything before, and might be reachable with a complete reimplementation of the machine.

Regards,
ralf

Re: Challenge "Sigaba Part 1"  

  By: stamp on Oct. 27, 2010, 5:44 p.m.

Hi Ralf,

maybe the wording in the challenge text is a little bit confusing but the given plaintext appears AT THE BEGINNING of the searched plaintext. Otherwise why should the file be called wwiiINITplain.txt???
And so it is feasible to resolve this challenge and it is definetly a Level 2 challenge…

Good Luck!
Pascal

Yes, the given plaintext, "WE THE ", is the initial 7 characters of the plaintext. Sorry for any confusion about that.

Mark Stamp

Re: Challenge "Sigaba Part 1"  

  By: Schoetti on Oct. 28, 2010, 12:36 p.m.

Now you even got one more character then in the challenge description… [HTML_REMOVED]

Pascal

Re: Challenge "Sigaba Part 1"  

  By: rwst on Nov. 6, 2010, 12:22 p.m.

Hello, it's me again.
The C code does not decrypt output from the Sigaba simulator:
http://cryptocellar.org/simula/sigaba/

Provided at least one of the cipher/control rotors is reversed!
This is, I believe, due to a faulty implementation of reverse
rotors in the C code.
I have confirmed the simulator does it right by following the
signal of the rightmost control rotor (set to #9) which is shown in
the attached picture.

I will continue solving to the C code, regardless if its implementation
is correct.

Regards,
ralf

Re: Challenge "Sigaba Part 1"  

  By: rr on Nov. 8, 2010, 12:26 a.m.

Hello,

I followed another approach to decrypt the message, but came to the same conclusion as rwst:
I think your program behaves differently than the real SIGABA (CSP-889).

Could you please clarify why there are differences from the results of your program to e.g. the simulator mentioned above?

Thanks

Re: Challenge "Sigaba Part 1"  

  By: rr on Nov. 16, 2010, 2:10 p.m.

Any news on this?

My efforts are completely useless if the message can only be decrypted with your program…

Re: Challenge "Sigaba Part 1"  

  By: Schoetti on Dec. 2, 2010, 11:01 a.m.

Hi!
Sorry for being late with the answer but it seems that Prof. Stamp, the author of the given Sigaba-Code, has a great deal of other work to do.
I would say that you should try to solve the challenge with the given C imlementation of the Sigaba cipher, since, of course, the given ciphertext was encrypted with the given code. And it should be clear, that if the code behaves different than an other simulator the output (either with enc- or decryption) is different as well.

Sorry for the inconvenience, maybe Mr. Stamp can have a look an the mentioned differences in the behaviour of the simulation software and can tell you why this happens.

Regards,

Pascal

Re: Challenge "Sigaba Part 1"  

  By: be on Dec. 20, 2010, 8:29 p.m.

Any news on this?

Prof. Stamp confirmed, that his student's program behaves differently than the real SIGABA. The reversed rotors don't work correct. But, it doesn't really effect the attack, as long as you use the given source code of the (apparently flawed) simulator.

If you succeed with this variant you are close to attack messages from unflawed sigaba simulators.

Re: Challenge "Sigaba Part 1"  

  By: madness on Aug. 7, 2023, 4:30 p.m.

Can somone please confirm that the given information about the key is used by the C code in this way:

./Sigaba ..........01234 .......... ABCDEZYXWV4.... 1 WWIIcipher.txt output.txt

where the dots are missing bits that we must find.

Edit: YES, that is how it works.

Maybe I have an old PDF, but it says "one of the 5 control rotors is ZYXWV".

Thank you in advance.

 Last edited by: madness on Aug. 7, 2023, 5:03 p.m., edited 1 time in total.

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