Extensions to DESthat may give a longer effective key

Tripe-DES: ciphertext =

EncDESk1(EncDESk2(EncDESk3( plaintext)))

EncDESk1(DecDESk1 xor k2(EncDESk2( plaintext)))

DESX: ciphertext = k1 xor EncDESk1(message xor k3)

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