Question

D cstnbe me Youun cv ewh gure nl et

Answer 1

Oata Encryption Standard A DES Round 32 bits Rn 32 bits L 48 bits One RoundMangler Eneryption Function 48 bits K; xe 2 bits 32 bits L 32 bits n

D E S has 16 rounds of operation. Each D E S round has the same operations and uses a different per round key. Each D E S round takes as input the server text produced by the previous round and outputs text for the next round. The input is divided into the left half and the right half. The output left half is just the right half of the input. The right half of the output is a result of XOR   the left half of the input and the output of the Mangler function. The Mangler function takes this input,the 32 bit input right half, expands it to 48 bits, then XOR it with the 48 bit program key. Then use the s-boxes to substitute the 48 bit value into a 32 bit value. We can also use algebra to represent in a D E S round, can be expressed as

L _n+1 =R _n   (output left half is just the right half of the input)

   R _n+1 =L n XOR M(R _n, K _n) (The right half of the output is a result of XOR the left half of the input and the output of the Mangler function)