Alleged IDEA(tm) Weakness

[Eric Cordian]

> I think this is wrong. It claims that the problem
> in IDEA comes from the bias of the multiplication
> operation... but the multiply in IDEA is over the
> integers modulo 65537, with the 0 value
> representing 65536, not 0...  this is in fact an
> unbiased operation. However I have not attempted
> to verify the rest of the logic.

Correct, multiplication by a non-zero residue modulo 65537 is a
permutation of the non-zero residues.  The central notion behind IDEA is
to use this operation, which can be expressed expeditiously in terms of
the unsigned 16x16->32 multiply, as a builtin wide S-Box.  This is how
IDEA manages to do strong encryption using only a few ordinary arithmetic
and logical instructions with no necessity for table lookup.

I didn't bother to read the rest of the rant. 

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