Encryption and decryption process

1. Write short notes on S-DES key generation process.

2. Explain about S-DES encryption and decryption process in detail.

3. What is the difference between a block cipher and a stream cipher?

Data Encryption

4. What is the purpose of the S-boxes in DES?

1. What is the total number of exclusive-or operations used in DES?

2. What is the purpose of the permutation in DES?

3. Explain about single round operation of DES in detail.

Consider a cipher composed of 16 rounds with an input bit block length of 64 bits and a key length of 64 bits. Input bits: 10101010 10101010 10101010 10101010 10101010 10101010 10101010 10101010; Key bits: 00111011 00111000 10011000 00110111 00010101 00100000 11110111 01011110. From the input bits and keys, find out the first eight round sub-keys.

Solution: