1
$\begingroup$

I have been studying the Diff. Cryptanalysis and finding it hard to do a problem. The problem is enter image description here

I have calculated the tables programmatically and found that the second table has a max value of 6 where as the first has a max value of 4.What can i infer from the tables? PS:I started reading this recently and need help in atleast the direction to think

$\endgroup$
  • $\begingroup$ I wrote my own testing software, I will check it within the hour $\endgroup$ – Richie Frame Aug 27 '14 at 3:37
1
$\begingroup$

Your calculations are correct. The 2nd table has 2 entries of 6 in its DDT, and 18 entries of 4. The Hamsi s-box has 24 entries of 4.

What can you infer from these tables? First off, CryptWizard001 is a liar. Second, the larger the max value in the DDT, the more vulnerable the s-box is to differential cryptanalysis, therefore the modified s-box does not have better differential properties.

For reference, here are the DDTs for both:

Hamsi
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 2 0 2 0 0 2 2 2 0 4 2 
0 0 0 4 0 4 0 0 0 4 0 0 0 0 0 4 
0 4 2 0 0 0 2 0 0 2 0 0 2 0 2 2 
0 0 0 0 0 0 4 0 0 0 4 4 0 4 0 0 
0 4 0 2 2 2 2 0 2 0 0 0 2 0 0 0 
0 0 2 2 2 2 0 0 2 2 0 0 0 0 2 2 
0 0 0 0 4 2 0 2 0 0 2 2 2 0 0 2 
0 0 0 2 0 2 0 4 0 2 0 0 0 4 0 2 
0 0 0 2 0 0 0 2 4 2 2 2 2 0 0 0 
0 0 2 0 2 0 4 0 2 0 4 0 0 0 2 0 
0 4 0 0 2 0 2 0 2 2 0 0 2 0 0 2 
0 0 2 0 2 0 0 0 2 0 0 4 0 4 2 0 
0 4 2 2 0 2 2 0 0 0 0 0 2 0 2 0 
0 0 2 0 2 0 0 4 2 0 0 0 0 4 2 0 
0 0 4 2 0 0 0 2 0 2 2 2 2 0 0 0 

Note I have left the upper left entry as 0, as it has a value of 16 and is ignored during analysis.

Modified
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 2 2 0 0 0 0 4 4 0 0 2 2 
0 0 0 0 0 2 0 2 0 4 0 4 0 2 0 2 
0 4 4 0 0 2 2 0 0 0 0 0 2 0 0 2 
0 0 0 2 0 2 4 0 0 0 2 0 0 2 2 2 
0 2 0 2 2 2 0 0 2 2 0 0 2 0 2 0 
0 2 0 2 2 0 2 0 2 2 0 0 0 0 2 2 
0 0 0 2 2 2 0 2 0 0 2 0 4 0 0 2 
0 0 0 4 0 0 0 4 0 4 0 0 0 4 0 0 
0 0 2 4 0 0 0 2 6 0 0 0 0 2 0 0 
0 0 6 0 2 0 0 0 2 0 4 0 0 0 2 0 
0 4 0 0 0 2 2 0 4 0 0 0 2 0 0 2 
0 0 0 0 2 0 2 0 0 2 2 4 2 2 0 0 
0 2 2 0 2 2 2 2 0 0 0 0 0 2 2 0 
0 2 2 0 2 0 0 2 0 0 0 0 2 2 2 2 
0 0 0 0 0 0 2 2 0 2 2 4 2 0 2 0 
| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.