DATA ENCRYPTION STANDARD DES Sheetal Thapaliya Outline History

  • Slides: 29
Download presentation
DATA ENCRYPTION STANDARD (DES) -Sheetal Thapaliya

DATA ENCRYPTION STANDARD (DES) -Sheetal Thapaliya

Outline History n Key Generation n Encryption n Decryption n Strength of DES n

Outline History n Key Generation n Encryption n Decryption n Strength of DES n Ultimate n

History In 1971, IBM developed an algorithm, named LUCIFER which operates on a block

History In 1971, IBM developed an algorithm, named LUCIFER which operates on a block of 64 bits, using a 128 -bit key Walter Tuchman, an IBM researcher, refined LUCIFER and reduced the key size to 56 -bit, to fit on a chip.

History In 1977, the results of Tuchman’s project of IBM was adopted as the

History In 1977, the results of Tuchman’s project of IBM was adopted as the Data Encryption Standard by NSA (NIST).

DES – Block Diagram

DES – Block Diagram

DES – Basic Information Block size of 64 bit n Usable Key size 56

DES – Basic Information Block size of 64 bit n Usable Key size 56 bit n Input = Plain text and Key n ¨ Plain text: 0000 0001 0010 0101 0110 0111 1000 1001 1010 1011 1101 1110 1111 ¨ Key: 000100110100 010101111001101111100 110111110001 Output = Cipher n No. of round = 16 n

Key Generation Input= 56 (or 64 bit) n Output = 16 subkey of 48

Key Generation Input= 56 (or 64 bit) n Output = 16 subkey of 48 bit n Uses Permuted Choice (PC-1) table n

Key Generation

Key Generation

Key Generation

Key Generation

Key Generation Generate other C 0 and D 0 by Left Circular Shift n

Key Generation Generate other C 0 and D 0 by Left Circular Shift n

Key Generation

Key Generation

Key Generation C 1 D 1 = 111000 1100110 0101010 1011111 1010101 01100111100 0011110

Key Generation C 1 D 1 = 111000 1100110 0101010 1011111 1010101 01100111100 0011110 K 1 = 000110 110000 00101111 111111 000001 110010

Key Generation

Key Generation

En. CRYption Input= 64 bit n Output = 64 bit n Key Size =

En. CRYption Input= 64 bit n Output = 64 bit n Key Size = 32 bit n

Encryption Block Diagram

Encryption Block Diagram

Encryption – IP (initial Permutation)

Encryption – IP (initial Permutation)

Encryption : Divide plain text

Encryption : Divide plain text

Encryption: The f function Block Diagram

Encryption: The f function Block Diagram

Encryption : Calculation of f Size Rn-1 = 32 bit Size of Kn =

Encryption : Calculation of f Size Rn-1 = 32 bit Size of Kn = 48 bit Thus Expand Rn-1 using E Bit-Selection Table

Encryption: Calculation of f E bit Selection Table

Encryption: Calculation of f E bit Selection Table

Encryption: Calculation of f S-Box Input = 6 bit X 8 = 48 bit

Encryption: Calculation of f S-Box Input = 6 bit X 8 = 48 bit Output= 4 bit X 8 = 32 bit Eg. : 011000 0101

Encryption: Calculation of f S-Box 010001 1100 011111 ?

Encryption: Calculation of f S-Box 010001 1100 011111 ?

Encryption: Calculation of f S-Box

Encryption: Calculation of f S-Box

Encryption: Calculation of f Output of S-BOX

Encryption: Calculation of f Output of S-BOX

Encryption: Calculation of f Last step: Permulation

Encryption: Calculation of f Last step: Permulation

Encryption: Final Calculation of R 1 Repeat this step upto 16 round Final block

Encryption: Final Calculation of R 1 Repeat this step upto 16 round Final block : L 16 Reverse to get : R 16 L 16

Encryption: Final Permutation

Encryption: Final Permutation

Encryption: Final Permutation

Encryption: Final Permutation

Thank you

Thank you