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, die@die.com DIE Consulting, Weston, Mass. PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2 5D 27 BD B0 24 88 C3 18