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Re: Nx2 DES Found Weak

	
> How is this different from a birthday attack ?

In Nx2 DES, you have   A -k1-> B -k2-> C .
In a birthday attack, you try values of k1' and k2' until you get k1', k2' s.t.
	E(A,k1') = B' = D(C,k2')
but that's only true for that particular plaintext set A,C.  
If you have B' = the same value of B that the original k1,k2 produced, you win,
but there may be many other values of B' besides the one for k1'=k1, k2'=k2.