Answer to Question #286158 in Computer Networks for sandhu

Question

What is the output of the first round of the DES algorithm when the plaintext and the key

are both all ones?

Answer 1

What is the output of the first round of the DES algorithm when the plaintext and the key

Answer:

DES- in full is Data Encryption standard. We should know that each round of DES takes a 64-bit(two 32-bit half blocks)and a 56-bit secret key. It is a symmetric key algorithm, which means that the same key is used for encrypting and decrypting data.64 message bit is the same as 16 hexadecimal numbers.

The output of first round of the DES algorithm when the plaintext and the key are all Zeros

Binary 0001=hexadecimal number “1”,1000 is equal to hexadecimal number”8”1001 = hexadecimal number “9”,1010= hexadecimal number “A”and 1111 = hexadecimal “F”.

Let M be plain text=0123456789ABCDEF where M is base 16 format

Rewriting M in binary format=0000,0001,0010,0011,0100,0101,0110,0111,1000,1001,1010,1011,1100,1101,1110,1111.The first bit of M is zero and the last bit of M is 1.

The 64-bit input is x0=000000000000000…..(64 Zeros)

L0=000…………(32 Zeros)

R0=000…….(32-zeros) this is the case where plain text and the key are zeros. But by the question above the plain text is all ones in this one the answer is the same but it is inverted.

NB: The output of R1 is the same as the output of R0 but it is inverted.