Question: DES(Data Encryption Standard)
Answer :
DES means Data Encryption Standard
Type : Block Cipher
Block Size : 64-bit
Key-Size: 64-bit, with only 56-bit effective
Number Of Rounds : 16
First the 64-bit plaintext passes through an initial permutation(IP) that rearrange the bits to produce the permuted input.
This is followed by a phase consisting of sixteen rounds of the same function which involves both permutation and substitution functions.
Finally the preoutput is passed through a permutation that is the inverse of the initial permutation function, to produce the 64-bit ciphertext.
The 56-bit key is passed through a permutation function.
For each of the sixteen rounds, a subkey(Ki) is produced by the combination of a left circular shift and a permutation.
Initial and inverse permutation :
The initial permutation of the DES algorithm changes the order of the plaintext before to the first round of the encryption.
The final permutation occurs after the sixteen rounds of DES are completed. it is the inverse of the initial permutation.
1) The Expansion Function E
2) Add Round Key
3) The DES S-Boxes
4) The Permutation P
Put random value 1 to 32.
