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Challenge "ORYX Stream Cipher Part I"  

  By: admin on July 21, 2010, 1:04 p.m.

The ORYX stream cipher consists of three 32-bit LFSRs X, A, B which are shifted differently depending on some bits in the LFSR X. The key stream is a combination of the highest 8 bits of each of the three LFSRs. It is neither feasible nor necessary to search the whole 96-bit key space, there are more efficient methods!Hint: Enter the codeword in hex with non-capital letters.
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 Last edited by: admin on Oct. 31, 2021, 2:54 a.m., edited 1 time in total.

Re: Challenge "ORYX Stream Cipher Part I"  

  By: fretty on Aug. 19, 2011, 7:45 p.m.

Can I have some clarification on this one.

Do the LFSR's shift to the right as the usually do with the ORYX cipher?

Also are we taking the first or the last 8 bits each time?

It is just that I have been looking this up in Mark Stamp's book (which is amazing) and running the attack mentioned there with veselovský…but after 4 iterations there are NO survivors.

We need to know whether our program is wrong or whether the cipher is operating differently in this challenge than in the book.

Re: Challenge "ORYX Stream Cipher Part I"  

  By: Veselovský on Aug. 20, 2011, 6:34 p.m.

[HTML_REMOVED]

Re: Challenge "ORYX Stream Cipher Part I"  

  By: akurei on Dec. 10, 2012, 3:17 p.m.

Same here, after the 4th keystream-byte (keyStream[3]) there are no survivors.

I went trough my code several times… No luck.
Can anyone give a hint what to do?

Challenge "ORYX Stream Cipher Part I"  

  By: Theofanidis on Jan. 7, 2013, 3:49 p.m.

Hello everybody

Is there a possibility that one volunteers to check my findings of the sequence of X,A,B registers because i came up to one survivor that works fine up to the 9th keystream but "dies" after this keystream, which is not consistent because this way one cannot find the initial fillings and so on. The program that i have made worked exactly for the whole data that accompany the program. I also assume that the L-permutation table is the same as the one with the program ?

If this volunteer is found i will send him/her a PM

Thanks in advance

Best regards
George

Re: Challenge "ORYX Stream Cipher Part I"  

  By: stamp on Jan. 11, 2013, 4:21 p.m.

George,

That sounds kind of strange. If you send me your X,A,B register fills, I'd be glad to take a quick look.

Mark Stamp

Re: Challenge "ORYX Stream Cipher Part I"  

  By: akurei on Feb. 27, 2013, 5:37 p.m.

I finally solved this. My mistake was to calculate in mod 0xff instead of 0x100 …

Re: Challenge  

  By: fmoraes on Nov. 25, 2013, 8:16 p.m.

I am sure I solved it correctly as I have the initial values but my input is not being accepted. I am sending a PM just in case.

Francisco

Re: Challenge  

  By: fmoraes on Nov. 26, 2013, 3:35 p.m.

I am sure I solved it correctly as I have the initial values but my input is not being accepted. I am sending a PM just in case.

Francisco

Got the right format with the help of a previous solver.

Francisco


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