1. DATA ENCRYPTION STANDARD (DES)
-Sheetal Thapaliya

2. Outline History Key Generation Encryption Decryption Strength of DES
Ultimate

3. 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.

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

5. DES – Block Diagram

6. DES – Basic Information
Block size of 64 bit
Usable Key size 56 bit
Input = Plain text and Key
Plain text:
Key:
Output = Cipher
No. of round = 16

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

8. Key Generation

9. Key Generation

10. Key Generation
Generate other C0 and
D0 by Left Circular Shift

11. Key Generation

12. Key Generation
C1D1 =
K1 =

13. Key Generation

14. EnCRYption
Input= 64 bit
Output = 64 bit
Key Size = 32 bit

15. Encryption Block Diagram

16. Encryption – IP (initial Permutation)

17. Encryption : Divide plain text

18. Encryption: The f function Block Diagram

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

20. Encryption: Calculation of f E bit Selection Table

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

22. Encryption: Calculation of f S-Box
1100 ?

23. Encryption: Calculation of f S-Box

24. Encryption: Calculation of f Output of S-BOX

25. Encryption: Calculation of f Last step: Permulation

26. Encryption: Final Calculation of R1
Repeat this step upto 16 round
Final block : L16 R16
Reverse to get : R16 L16

27. Encryption: Final Permutation

28. Encryption: Final Permutation

29. Thank you