Long description

The high level illustration of the D E S cipher passed through 10 different steps which are as follows. Step 0: Sixteen 48 bit keys are generated from the 64 bit shared key that reads, 1 1 1 0 1 0 0 1 0 1 1 0 ellipsis. The 48 bit keys are read as Sub key 1, Sub key 2, and so on till sub key 16.

Step 1: Message is broken into 64 bit blocks open parenthesis and padded out close parenthesis. The 64 bit blocks read as follows. 0 1 0 0 0 1 0 1 0 1 0 1 ellipsis. 1 1 1 0 1 1 0 0 0 0 1 ellipsis. 0 1 1 0 1 0 1 0 1 1 1 ellipsis.

Step 2: For each 64 bit block.

Step 3: The block is split into two 32 bit blocks.

The first 64 bit block in step 1 is split into 2 blocks. Block 1: 1 1 1 0 1 0 1 1 0 0 1. Block 2: 0 1 0 0 0 1 0 1 0 1 0 1.

Step 4: The 32 bit value is expanded to 48 bits and X O R'd with the key for this round. Block 2 is X O R’d with sub key i.

Step 5: The X O R'd value is split into 8 and 6 bit blocks and run through the eight S boxes open parenthesis Substitution boxes close parenthesis. The sub key i is split into S 1, S2, and so on till S 8.

Step 6: The permuted blocks are recombined. The permuted blocks are recombined as 0 1 0 1 1 1 0 0 0 1 0 0 ellipsis.

Step 7: The scrambled 32 bit value is X O R'd with the other 32 bit block. Block 1 is X O R’d with the permuted block as 1 0 1 1 0 1 1 1 1 0 1 0 1 ellipsis.

Step 8: The 32 bit blocks are switched for the next round, go back to Step 4.

Step 9: After 16 rounds we have the scrambled 64 bit value open parenthesis the cipher text close parenthesis.