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Re: DESX



On Sun, Oct 11, 1998 at 12:06:14AM +0200, Anonymous wrote:
> | So what's DESX?
> 
> DESX is a modification of DES which uses a 64+56+64 bit key, with
> what is called "pre- and post-whitening".  Specifically, break the key
> into three pieces, 64 bit K1, 56 bit K2, 64 bit K3.  Then DESX is
> defined by:
> 
> 	C = K1 xor DES (K2, K3 xor P)
> 
> where P is plaintext, C is ciphertext, and DES (K, P) is the DES
> encryption of P under key K.
> 
> The encryption then has three steps:
> 
> 	- XOR the input with K3
> 	- DES encrypt that with K2
> 	- XOR the result with K1
> 
> The first and last steps are called "whitening" because by xoring with
> a random value, any structure is destroyed.  White light is a uniform
> and unstructured mixture of all colors.
> 

	Anybody have any estimate as to how much actual strength this
adds to DES ?  How would one break it in a practical cracker machine ?





-- 
	Dave Emery N1PRE,  [email protected]  DIE Consulting, Weston, Mass. 
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2  5D 27 BD B0 24 88 C3 18