Feistel cipher
- 2. PRESENTATION ON FEISTEL ENCRYPTION AND DECRYPTIPON Presented By :- Md.Kawsar Ahmed Dept. of ICE,PUST
- 3. CONTENT Feistel Cipher Structure Diagram of Feistel Network Design Features of Feistel Network The Function
- 4. FEISTEL CIPHER STRUCTURE Horst Feistel devised the feistel cipher based on concept of invertible product cipher Partitions input block into two halves process through multiple rounds which perform a substitution on left data half based on round function of right half & sub key then have permutation swapping halves Implements Shannon’s substitution-permutation network concept
- 5. FEISTEL CIPHER STRUCTURE All rounds have the same structure A substitution is performed on the left half of the data. This is done by applying a round function to the right half of the data followed by the XOR of the output of that function and the left half of the data.
- 6. DIAGRAM OF FEISTEL NETWORK FIGURE-01: FEISTEL ENCRYPTION PROCESS
- 7. DIAGRAM OF FEISTEL ENCRYPTION AND DECRYPTION FIGURE-02: FEISTEL ENCRYPTION AND DECRYPTION
- 8. DESIGN FEATURES OF FEISTEL NETWORK Block Size: Increasing size improves security but slow cipher. Key Size: Increasing size improves security, makes exhaustive key searching harder but may slow cipher. Number of Rounds: Increasing number improves security but slow cipher. Sub-key Generation: Greater complexity can make analysis harder but slow cipher. Round function: Greater complexity can make analysis harder but slow cipher. Decryption: Use the same algorithm with reversed keys.
- 9. THE FUNCTION Let L and R be the left most 4 bits and rightmost 4 bits of the 8 bits input f(L, R)=(LF(R,SK),R) Where SK is a sub key and the is bit-by-bit XOR function. Ex: if the plaintext is (10111101) and F(1101,SK)=(1110) for some SK then f(10111101)=(1011) (1110)=(0101)
- 10. THANK YOU VERY MUCH