Consider the two S-boxes S1 and S2 of DES shown. Three hex digits (12 bits) are

Question

Consider the two S-boxes S1 and S2 of DES shown. Three hex digits (12 bits) are provided to these two S boxes. The higher order six bits are fed to S1 and the lower order six bits are fed to S2. For the six bits input to S1, the first and last bits are used to select the row, and the middle four bits are used to select the column. Note that each S box has four rows numbered 0, 1, 2, and 3 and sixteen columns numbered O to 15. So, two bits are sufficient to select a row, as 22 4 and four bits are sufficient to select column, as 24-16. The output from each S box is a four bit binary number, which means that the output from each S box ranges from O to 15 1 CO C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 RO 15 12 82 4917 5 11 3 14 100 6 13 R114 4 13 1 2 15 11 8 3 10 6 12 5 907 R2 015 7 4 14 213 1 10 6 12 1195 3 8 R34 1 14 8 13 6 2 1115 129 7 3 10 5 0 S2 CO C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 RO 13 8 10 1 3 15 4 2 116 7 12 0 5 14 9 R1 15 1 8 14 6 11 3 4 97 2 13 12 0 5 10 R2 0 14 7 1110 413 1 5 8 12 693 2 15 R3 3 1347 15 2 8 14 12 0 1 10 6 9 11 5 Given the 12 bit hex input of 94216 - calculate the S1 & S2 outputs. Express your answer in hexadecimal 0 7E ED E8 DE

Explanation / Answer

The number in hex is 942== 100101 000010

Hence for s1 we have 11 as the row number in binary i.e row 3 and the column number will be 2 Hence the output is E in hex

and

For S2 it will be row 0 and column 1 which gives us the output 8

Hence the output is E8

Do give a thumbs up

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---